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LT1207 Dual 250mA/60MHz Current Feedback Amplifier
FEATURES
s s s s s s s s
DESCRIPTIO
250mA Minimum Output Drive Current 60MHz Bandwidth, AV = 2, RL = 100 900V/s Slew Rate, AV = 2, RL = 50 0.02% Differential Gain, AV = 2, RL = 30 0.17 Differential Phase, AV = 2, RL = 30 High Input Impedance: 10M Shutdown Mode: IS < 200A per Amplifier Stable with CL = 10,000pF
APPLICATIO S
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ADSL/HDSL Drivers Video Amplifiers Cable Drivers RGB Amplifiers Test Equipment Amplifiers Buffers
The LT (R) 1207 is a dual version of the LT1206 high speed current feedback amplifier. Like the LT1206, each CFA in the dual has excellent video characteristics: 60MHz bandwidth, 250mA minimum output drive current, 400V/s minimum slew rate, low differential gain (0.02% typ) and low differential phase (0.17 typ). The LT1207 includes a pin for an optional compensation network which stabilizes the amplifier for heavy capacitive loads. Both amplifiers have thermal and current limit circuits which protect against fault conditions. These capabilities make the LT1207 well suited for driving difficult loads such as cables in video or digital communication systems. Operation is fully specified from 5V to 15V supplies. Supply current is typically 20mA per amplifier. Two micropower shutdown controls place each amplifier in a high impedance low current mode, dropping supply current to 200A per amplifier. For reduced bandwidth applications, supply current can be lowered by adding a resistor in series with the Shutdown pin. The LT1207 is manufactured on Linear Technology's complementary bipolar process and is available in a low thermal resistance 16-lead SO package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATION
5V VIN SHDN A
HDSL Driver
+
0.1F* 2.2F**
+
1/2 LT1207
-
720 15k 240 720 720
62 L1
-
SHDN B 15k 1/2 LT1207
62
+ +
-5V 0.1F* 2.2F**
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* CERAMIC ** TANTALUM L1 = TRANSPOWER SMPT-308 OR SIMILAR DEVICE
1207 * TA01
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LT1207 ABSOLUTE AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW V+ 1 16 V+
Supply Voltage ..................................................... 18V Input Current per Amplifier ............................... 15mA Output Short-Circuit Duration (Note 1) ....... Continuous Specified Temperature Range (Note 2) ...... 0C to 70C Operating Temperature Range ............... - 40C to 85C Junction Temperature ......................................... 150C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec)................. 300C
ORDER PART NUMBER LT1207CS
-IN A 2 +IN A 3 SHDN A 4 -IN B 5 +IN B 6 SHDN B 7 V+ 8
15 OUT A 14 V - A 13 COMP A 12 OUT B 11 V - B 10 COMP B 9 V+
S PACKAGE 16-LEAD PLASTIC SO
JA = 40C/W (NOTE 3)
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
SYMBOL VOS PARAMETER Input Offset Voltage Input Offset Voltage Drift IIN+ IIN- en + in - in RIN CIN Noninverting Input Current Inverting Input Current Input Noise Voltage Density Input Noise Current Density Input Noise Current Density Input Resistance Input Capacitance Input Voltage Range CMRR Common Mode Rejection Ratio Inverting Input Current Common Mode Rejection PSRR Power Supply Rejection Ratio TA = 25C TA = 25C
VCM = 0, 5V VS 15V, pulse tested, VSHDN A = 0V, VSHDN B = 0V, unless otherwise noted.
CONDITIONS
q q q
MIN
TYP 3 10 2 10
MAX 10 15 5 20 60 100
UNITS mV mV V/C A A A A nV/Hz pA/Hz pA/Hz M M pF V V dB dB
TA = 25C
q
f = 10kHz, RF = 1k, RG = 10, RS = 0 f = 10kHz, RF = 1k, RG = 10, RS = 10k f = 10kHz, RF = 1k, RG = 10, RS = 10k VIN = 12V, VS = 15V VIN = 2V, VS = 5V VS = 15V VS = 15V VS = 5V VS = 15V, VCM = 12V VS = 5V, VCM = 2V VS = 15V, VCM = 12V VS = 5V, VCM = 2V VS = 5V to 15V
q q q q q q q q q
3.6 2 30 1.5 0.5 12 2 55 50 10 5 2 13.5 3.5 62 60 0.1 0.1 60 77 10 10
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A/V A/V dB
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LT1207
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER Noninverting Input Current Power Supply Rejection Inverting Input Current Power Supply Rejection AV ROL VOUT Large-Signal Voltage Gain Transresistance, VOUT/IIN- Maximum Output Voltage Swing
VCM = 0, 5V VS 15V, pulse tested, VSHDN A = 0V, VSHDN B = 0V, unless otherwise noted.
CONDITIONS VS = 5V to 15V VS = 5V to 15V VS = 15V, VOUT = 10V, RL = 50 VS = 5V, VOUT = 2V, RL = 25 VS = 15V, VOUT = 10V, RL = 50 VS = 5V, VOUT = 2V, RL = 25 VS = 15V, RL = 50, TA = 25C VS = 5V, RL = 25, TA = 25C
q q q q q q q q
MIN
TYP 30 0.7
MAX 500 5
UNITS nA/V A/V dB dB k k V V V V
55 55 100 75 11.5 10.0 2.5 2.0 250
71 68 260 200 12.5 3.0 500 20 1200 30 35 17 200 10
IOUT IS
Maximum Output Current Supply Current per Amplifier Supply Current per Amplifier, RSHDN = 51k (Note 4) Positive Supply Current per Amplifier, Shutdown Output Leakage Current, Shutdown
RL = 1 VS = 15V, VSHDN = 0V, TA = 25C
q q
mA mA mA mA A A V/s % DEG MHz MHz MHz MHz
VS = 15V, TA = 25C VS = 15V, VSHDN A = 15V, VSHDN B = 15V VS = 15V, VSHDN = 15V, VOUT = 0V AV = 2, TA = 25C VS = 15V, RF = 560, RG = 560, RL = 30 VS = 15V, RF = 560, RG = 560, RL = 30 VS = 15V, Peaking 0.5dB RF = RG = 620, RL = 100 VS = 15V, Peaking 0.5dB RF = RG = 649, RL = 50 VS = 15V, Peaking 0.5dB RF = RG = 698, RL = 30 VS = 15V, Peaking 0.5dB RF = RG = 825, RL = 10
q q
12
SR
Slew Rate (Note 5) Differential Gain (Note 6) Differential Phase (Note 6)
400
900 0.02 0.17 60 52 43 27
BW
Small-Signal Bandwidth
The q denotes specifications which apply for 0C TA 70C. Note 1: Applies to short circuits to ground only. A short circuit between the output and either supply may permanently damage the part when operated on supplies greater than 10V. Note 2: Commercial grade parts are designed to operate over the temperature range of - 40C to 85C but are neither tested nor guaranteed beyond 0C to 70C. Industrial grade parts tested over - 40C to 85C are available on special request. Consult factory.
Note 3: Thermal resistance JA varies from 40C/W to 60C/W depending upon the amount of PC board metal attached to the device. JA is specified for a 2500mm2 test board covered with 2oz copper on both sides. Note 4: RSHDN is connected between the Shutdown pin and ground. Note 5: Slew rate is measured at 5V on a 10V output signal while operating on 15V supplies with RF = 1.5k, RG = 1.5k and RL = 400. Note 6: NTSC composite video with an output level of 2V.
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LT1207
S ALL-SIG AL BA DWIDTH
IS = 20mA per Amplifier Typical, Peaking 0.1dB
AV RL RF RG 562 649 732 - - - 576 649 750 48.7 56.2 71.5 - 3dB BW (MHz) 48 34 22 54 36 22.4 48 35 22.4 40 31 20 - 0.1dB BW (MHz) 21.4 17 12.5 22.3 17.5 11.5 20.7 18.1 11.7 19.2 16.5 10.2 AV RL RF RG 681 768 887 - - - 665 787 931 536 64.9 84.5 - 3dB BW (MHz) 50 35 24 66 37 23 55 36 22.5 44 33 20.7 - 0.1dB BW (MHz) 19.2 17 12.3 22.4 17.5 12 23 18.5 11.8 20.7 17.5 10.8
VS = 5V, RSHDN = 0 -1 150 562 30 649 10 732 1 150 619 30 715 10 806 2 150 576 30 649 10 750 10 150 442 30 511 10 649
IS = 10mA per Amplifier Typical, Peaking 0.1dB
AV RL RF RG 576 681 750 - - - 590 681 768 33.2 43.2 54.9 - 3dB BW (MHz) 35 25 16.4 37 25 16.5 35 25 16.2 31 23 15 - 0.1dB BW (MHz) 17 12.5 8.7 17.5 12.6 8.2 16.8 13.4 8.1 15.6 11.9 7.8 AV RL RF RG 634 768 866 - - - 649 787 931 33.2 44.2 64.9 - 3dB BW (MHz) 41 26.5 17 44 28 16.8 40 27 16.5 33 25 15.3 - 0.1dB BW (MHz) 19.1 14 9.4 18.8 14.4 8.3 18.5 14.1 8.1 15.6 13.3 7.4
VS = 5V, RSHDN = 10.2k -1 150 576 30 681 10 750 1 150 665 30 768 10 845 2 150 590 30 681 10 768 10 150 301 30 392 10 499
IS = 5mA per Amplifier Typical, Peaking 0.1dB
AV -1 RL 150 30 10 150 30 10 150 30 10 150 30 10 RF 604 715 681 768 866 825 634 750 732 100 100 100 RG 604 715 681 - - - 634 750 732 11.1 11.1 11.1 - 3dB BW (MHz) 21 14.6 10.5 20 14.1 9.8 20 14.1 9.6 16.2 13.4 9.5 - 0.1dB BW (MHz) 10.5 7.4 6.0 9.6 6.7 5.1 9.6 7.2 5.1 5.8 7.0 4.7 AV -1 RL 150 30 10 150 30 10 150 30 10 150 30 10 RF 619 787 825 845 1k 1k 681 845 866 100 100 100 RG 619 787 825 - - - 681 845 866 11.1 11.1 11.1 - 3dB BW (MHz) 25 15.8 10.5 23 15.3 10 23 15 10 15.9 13.6 9.6 - 0.1dB BW (MHz) 12.5 8.5 5.4 10.6 7.6 5.2 10.2 7.7 5.4 4.5 6 4.5
VS = 5V, RSHDN = 22.1k
1
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VS = 15V, RSHDN = 0 -1 150 681 30 768 10 887 1 150 768 30 909 10 1k 2 150 665 30 787 10 931 10 150 487 30 590 10 768
VS = 15V, RSHDN = 60.4k -1 150 634 30 768 10 866 1 150 768 30 909 10 1k 2 150 649 30 787 10 931 10 150 301 30 402 10 590
VS = 15V, RSHDN = 121k
1
2
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LT1207
TYPICAL PERFOR A CE CHARACTERISTICS
Bandwidth vs Supply Voltage
100 90 PEAKING 0.5dB PEAKING 5dB RF = 470 RF = 560 RF = 680 AV = 2 RL = 100
-3dB BANDWIDTH (MHz)
FEEDBACK RESISTOR ()
- 3dB BANDWIDTH (MHz)
80 70 60 50 40 30 20 10 0 4 6 14 12 10 8 SUPPLY VOLTAGE (V) 16 18 RF = 1k RF = 1.5k RF = 750
LT1207 * TPC01
Bandwidth vs Supply Voltage
100 90 PEAKING 0.5dB PEAKING 5dB AV = 10 RL = 100
- 3dB BANDWIDTH (MHz)
-3dB BANDWIDTH (MHz)
80 70 60 50 40 30 20 10 0 4 6 14 12 10 8 SUPPLY VOLTAGE (V) 16 18 RF = 680 RF = 1.5k RF = 470 RF =390 RF = 330
FEEDBACK RESISTOR ()
LT1207 * TPC04
Differential Phase vs Supply Voltage
0.50 RL = 15
DIFFERENTIAL GAIN (%)
DIFFERENTIAL PHASE (DEG)
0.40
0.08
RL = 15
SPOT NOISE (nV/Hz OR pA/Hz)
0.30
0.20
RF = RG = 560 AV = 2 N PACKAGE
RL = 30 RL = 50 RL = 150
0.10
0 5 7 11 13 9 SUPPLY VOLTAGE (V) 15
LT1207 * TPC07
UW
Bandwidth vs Supply Voltage
50 PEAKING 0.5dB PEAKING 5dB 40 RF = 560 30 RF = 750 RF = 1k RF = 2k 10 AV = 2 RL = 10
Bandwidth and Feedback Resistance vs Capacitive Load for 0.5dB Peak
10k BANDWIDTH
-3dB BANDWIDTH (MHz)
100
1k FEEDBACK RESISTOR AV = 2 RL = VS = 15V CCOMP = 0.01F 1 100 10 1000 CAPACITIVE LOAD (pF)
10
20
0 4 6 14 12 10 8 SUPPLY VOLTAGE (V) 16 18
100
1 10000
LT1207 * TPC02
LT1207 * TPC03
Bandwidth vs Supply Voltage
50 PEAKING 0.5dB PEAKING 5dB 40 AV = 10 RL = 10
Bandwidth and Feedback Resistance vs Capacitive Load for 5dB Peak
10k BANDWIDTH 100
-3dB BANDWIDTH (MHz)
30
RF = 560 RF = 680 RF = 1k
1k
10
20
10
RF = 1.5k
FEEDBACK RESISTOR
0 4 6 14 12 10 8 SUPPLY VOLTAGE (V) 16 18
0 100 1
AV = +2 RL = VS = 15V CCOMP = 0.01F
10 100 1k CAPACITIVE LOAD (pF)
1 10k
LT1207 * TPC05
LT1207 * TPC06
Differential Gain vs Supply Voltage
0.10 RF = RG = 560 AV = 2 N PACKAGE
100
Spot Noise Voltage and Current vs Frequency
-in
0.06 RL = 30 0.04 RL = 50
10 en in 1 10
0.02 RL = 150 0 5 7 11 13 9 SUPPLY VOLTAGE (V) 15
100
1k 10k FREQUENCY (Hz)
100k
LT1207 * TPC09
LT1207 * TPC08
5
LT1207
TYPICAL PERFOR A CE CHARACTERISTICS
Supply Current vs Supply Voltage
24
SUPPLY CURRENT PER AMPLIFIER (mA)
22 20
TJ = -40C
SUPPLY CURRENT PER AMPLIFIER (mA)
SUPPLY CURRENT PER AMPLIFIER (mA)
VSHDN = 0V
TJ = 25C 18 16 14 TJ = 125C 12 10 4 6 14 12 10 8 SUPPLY VOLTAGE (V) 16 18 TJ = 85C
LT1207 * TPC10
Supply Current vs Shutdown Pin Current
20
SUPPLY CURRENT PER AMPLIFIER (mA)
18 16 14 12 10 8 6 4 2 0 0
- 0.5
OUTPUT SHORT-CIRCUIT CURRENT (A)
VS = 15V
COMMON MODE RANGE (V)
100 300 400 200 SHUTDOWN PIN CURRENT (A)
Output Saturation Voltage vs Junction Temperature
V+ OUTPUT SATURATION VOLTAGE (V) -1 -2 -3 -4 4 3 2 1 V- -50 -25 0 25 50 75 TEMPERATURE (C) 100 125 RL = 50 VS = 15V
POWER SUPPLY REJECTION (dB)
60 50 40 30 20 10 0 10k
NEGATIVE POSITIVE
SUPPLY CURRENT PER AMPLIFIER (mA)
RL = 2k RL = 50
RL = 2k
LT1207 * TPC16
6
UW
500
LT1207 * TPC13
Supply Current vs Ambient Temperature, VS = 5V
25 RSD = 0 AV = 1 RL =
25
Supply Current vs Ambient Temperature, VS = 15V
RSD = 0 20 AV = 1 RL =
20
15 RSD = 10.2k 10 RSD = 22.1k
15 RSD = 60.4k 10 RSD = 121k 5
5
0 -50 -25
50 25 0 75 TEMPERATURE (C)
100
125
0 -50 -25
50 25 0 75 TEMPERATURE (C)
100
125
LT1207 * TPC11
LT1207 * TPC12
Input Common Mode Limit vs Junction Temperature
V+
Output Short-Circuit Current vs Junction Temperature
1.0 0.9 0.8 SOURCING 0.7 0.6 SINKING 0.5 0.4 0.3 -50 -25
-1.0 -1.5 -2.0 2.0 1.5 1.0 0.5 V- -50 -25 0 25 50 75 TEMPERATURE (C) 100 125
50 25 75 0 TEMPERATURE (C)
100
125
LT1207 * TPC14
LT1207 * TPC15
Power Supply Rejection Ratio vs Frequency
70 RL = 50 VS = 15V RF = RG = 1k
60
Supply Current vs Large-Signal Output Frequency (No Load)
AV = 2 RL = VS = 15V VOUT = 20VP-P
50
40
30
20
100k
1M 10M FREQUENCY (Hz)
100M
LT1207 * TPC17
10 10k
100k
1M
10M
LT1207 * TPC18
FREQUENCY (Hz)
LT1207
TYPICAL PERFOR A CE CHARACTERISTICS
Output Impedance vs Frequency
100 VS = 15V IO = 0mA RSHDN = 121k 100k AV = 1 RF = 1k VS = 15V OUTPUT IMPEDANCE () 10k DISTORTION (dBc)
OUTPUT IMPEDANCE ()
10
1
RSHDN = 0
0.1
0.01 100k
1M
10M
FREQUENCY (Hz)
LT1207 * TPC19
3rd Order Intercept vs Frequency
60 VS = 15V RL = 50 RF = 590 RG = 64.9
3rd ORDER INTERCEPT (dBm)
50
40
30
20
10
0
5
UW
100M
Output Impedance in Shutdown vs Frequency
-30 -40 -50 -60 -70 -80
10 100k
2nd and 3rd Harmonic Distortion vs Frequency
VS = 15V VO = 2VP-P RL = 10 2nd 3rd 2nd
1k
RL = 30
100
3rd
-90
1M 10M 100M
LT1207 * TPC20
1
FREQUENCY (Hz)
3 2 45 FREQUENCY (MHz)
6 7 8 9 10
LT1207 * TPC21
Test Circuit for 3rd Order Intercept
+
1/2 LT1207 PO
-
590 65 MEASURE INTERCEPT AT PO
LT1207 * TPC23
50
10 15 20 FREQUENCY (MHz)
25
30
LT1207 * TPC22
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LT1207
SI PLIFIED SCHE ATIC
V+ TO ALL CURRENT SOURCES Q2 Q18 Q17 1.25k +IN Q1 Q6 Q9 V- RC 50 COMP OUTPUT V+ V+ Q12 Q8 Q4 Q7 D2 Q13 Q16 Q14 Q5 D1 Q15
APPLICATI
S I FOR ATIO
The LT1207 is a dual current feedback amplifier with high output current drive capability. The device is stable with large capacitive loads and can easily supply the high currents required by capacitive loads. The amplifier will drive low impedance loads such as cables with excellent linearity at high frequencies. Feedback Resistor Selection The optimum value for the feedback resistors is a function of the operating conditions of the device, the load impedance and the desired flatness of response. The Typical AC Performance tables give the values which result in the highest 0.1dB and 0.5dB bandwidths for various resistive loads and operating conditions. If this level of flatness is not required, a higher bandwidth can be obtained by use of a lower feedback resistor. The characteristic curves of Bandwidth vs Supply Voltage indicate feedback resistors for peaking up to 5dB. These curves use a solid line when the response has less than 0.5dB of peaking and a dashed
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Q10 Q11
V- -IN CC
SHUTDOWN
Q3
V- 1/2 LT1207 CURRENT FEEDBACK AMPLIFIER
LT1207 * SS
line when the response has 0.5dB to 5dB of peaking. The curves stop where the response has more than 5dB of peaking. For resistive loads, the COMP pin should be left open (see section on capacitive loads). Capacitive Loads Each amplifier in the LT1207 includes an optional compensation network for driving capacitive loads. This network eliminates most of the output stage peaking associated with capacitive loads, allowing the frequency response to be flattened. Figure 1 shows the effect of the network on a 200pF load. Without the optional compensation, there is a 5dB peak at 40MHz caused by the effect of the capacitance on the output stage. Adding a 0.01F bypass capacitor between the output and the COMP pins connects the compensation and completely eliminates the peaking. A lower value feedback resistor can now be used, resulting in a response which is flat to 0.35dB to 30MHz.
LT1207
APPLICATI
12 10 8
S I FOR ATIO
VS = 15V RF = 1.2k COMPENSATION
VOLTAGE GAIN (dB)
6 4 2 0 -2 -4 -6 -8 1
RF = 2k NO COMPENSATION RF = 2k COMPENSATION
10 FREQUENCY (MHz)
100
LT1207 * F01
Figure 1.
The network has the greatest effect for CL in the range of 0pF to 1000pF. The graph of Maximum Capacitive Load vs Feedback Resistor can be used to select the appropriate value of the feedback resistor. The values shown are for 0.5dB and 5dB peaking at a gain of 2 with no resistive load. This is a worst-case condition, as the amplifier is more stable at higher gains and with some resistive load in parallel with the capacitance. Also shown is the -3dB bandwidth with the suggested feedback resistor vs the load capacitance. Although the optional compensation works well with capacitive loads, it simply reduces the bandwidth when it is connected with resistive loads. For instance, with a 30 load, the bandwidth drops from 55MHz to 35MHz when the compensation is connected. Hence, the compensation was made optional. To disconnect the optional compensation, leave the COMP pin open. Shutdown/Current Set If the shutdown feature is not used, the Shutdown pins must be connected to ground or V -. Each amplifier has a separate Shutdown pin which can be used to either turn off the amplifier, which reduces the amplifier supply current to less than 200A, or to control the supply current in normal operation. The supply current in each amplifier is controlled by the current flowing out of the Shutdown pin. When the Shutdown pin is open or driven to the positive supply, the amplifier is shut down. In the shutdown mode, the output looks like a 40pF capacitor and the supply current is
ENABLE VOUT
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typically 100A. Each Shutdown pin is referenced to the positive supply through an internal bias circuit (see the Simplified Schematic). An easy way to force shutdown is to use open drain (collector) logic. The circuit shown in Figure 2 uses a 74C904 buffer to interface between 5V logic and the LT1207. The switching time between the active and shutdown states is less than 1s. A 24k pull-up resistor speeds up the turn-off time and insures that the amplifier is completely turned off. Because the pin is referenced to the positive supply, the logic used should have a breakdown voltage of greater than the positive supply voltage. No other circuitry is necessary as the internal circuit limits the Shutdown pin current to about 500A. Figure 3 shows the resulting waveforms.
15V VIN
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1/2 LT1207 SHDN -15V VOUT
RF
15V 5V ENABLE 74C906 24k
RG
LT1207 * F02
Figure 2. Shutdown Interface
AV = 1 RF = 825 RL = 50
RPU = 24k VIN = 1VP-P
LT1207 * F3
Figure 3. Shutdown Operation
For applications where the full bandwidth of the amplifier is not required, the quiescent current may be reduced by connecting a resistor from the Shutdown pin to ground.
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LT1207
APPLICATI S I FOR ATIO U
and for higher gains in the noninverting mode, the signal amplitude on the input pins is small and the overall slew rate is that of the output stage. The input stage slew rate is related to the quiescent current and will be reduced as the supply current is reduced. The output slew rate is set by the value of the feedback resistors and the internal capacitance. Larger feedback resistors will reduce the slew rate as will lower supply voltages, similar to the way the bandwidth is reduced. The photos (Figures 5a, 5b and 5c) show the large-signal response of the LT1207 or various gain configurations. The slew rate varies from 860V/s for a gain of 1, to 1400V/s for a gain of - 1. When the LT1207 is used to drive capacitive loads, the available output current can limit the overall slew rate. In the fastest configuration, the LT1207 is capable of a slew rate of over 1V/ns. The current required to slew a capacitor
RF = 825 RL = 50 VS = 15V
LT1207 * F05a
The amplifier's supply current will be approximately 40 times the current in the Shutdown pin. The voltage across the resistor in this condition is V + - 3VBE. For example, a 60k resistor will set the amplifier's supply current to 10mA with VS = 15V. The photos (Figures 4a and 4b) show the effect of reducing the quiescent supply current on the large-signal response. The quiescent current can be reduced to 5mA in the inverting configuration without much change in response. In noninverting mode, however, the slew rate is reduced as the quiescent current is reduced.
RF = 750 RL = 50
IQ = 5mA, 10mA, 20mA VS = 15V
Figure 4a. Large-Signal Response vs IQ, AV = -1
RF = 750 RL = 50
IQ = 5mA, 10mA, 20mA VS = 15V
Figure 4b. Large-Signal Response vs IQ, AV = 2
Slew Rate Unlike a traditional op amp, the slew rate of a current feedback amplifier is not independent of the amplifier gain configuration. There are slew rate limitations in both the input stage and the output stage. In the inverting mode,
VS = 15V
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LT1207 * F04a
Figure 5a. Large-Signal Response, AV = 1
LT1207 * F04b
RF = RG = 750 RL = 50
LT1207 * F05b
Figure 5b. Large-Signal Response, AV = -1
LT1207
APPLICATI S I FOR ATIO U
Capacitance on the Inverting Input Current feedback amplifiers require resistive feedback from the output to the inverting input for stable operation. Take care to minimize the stray capacitance between the output and the inverting input. Capacitance on the inverting input to ground will cause peaking in the frequency response (and overshoot in the transient response), but it does not degrade the stability of the amplifier. Power Supplies
RF = 750 RL = 50
LT1207 * F05c
Figure 5c. Large-Signal Response, AV = 2
at this rate is 1mA per picofarad of capacitance, so 10,000pF would require 10A! The photo (Figure 6) shows the large-signal behavior with CL = 10,000pF. The slew rate is about 60V/s, determined by the current limit of 600mA.
VS = 15V RF = RG = 3k
RL =
Figure 6. Large-Signal Response, CL = 10,000pF
Differential Input Signal Swing The differential input swing is limited to about 6V by an ESD protection device connected between the inputs. In normal operation, the differential voltage between the input pins is small, so this clamp has no effect; however, in the shutdown mode the differential swing can be the same as the input swing. The clamp voltage will then set the maximum allowable input voltage. To allow for some margin, it is recommended that the input signal be less than 5V when the device is shut down.
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The LT1207 will operate from single or split supplies from 5V (10V total) to 15V (30V total). It is not necessary to use equal value split supplies, however the offset voltage and inverting input bias current will change. The offset voltage changes about 500V per volt of supply mismatch. The inverting bias current can change as much as 5A per volt of supply mismatch, though typically the change is less than 0.5A per volt. Thermal Considerations Each amplifier in the LT1207 includes a separate thermal shutdown circuit which protects against excessive internal (junction) temperature. If the junction temperature exceeds the protection threshold, the amplifier will begin cycling between normal operation and an off state. The cycling is not harmful to the part. The thermal cycling occurs at a slow rate, typically 10ms to several seconds, which depends on the power dissipation and the thermal time constants of the package and heat sinking. Raising the ambient temperature until the device begins thermal shutdown gives a good indication of how much margin there is in the thermal design. Heat flows away from the amplifier through the package's copper lead frame. Heat sinking is accomplished by using the heat spreading capabilities of the PC board and its copper traces. Experiments have shown that the heat spreading copper layer does not need to be electrically connected to the tab of the device. The PCB material can be very effective at transmitting heat between the pad area attached to the tab of the device and a ground or power plane layer either inside or on the opposite side of the board. Although the actual thermal resistance of the PCB material is high, the length/area ratio of the thermal
LT1207 * F06
11
LT1207
APPLICATI S I FOR ATIO U
where: TJ = Junction Temperature TA = Ambient Temperature PD = Device Dissipation JA = Thermal Resistance (Junction-to-Ambient) As an example, calculate the junction temperature for the circuit in Figure 8 assuming a 70C ambient temperature. The device dissipation can be found by measuring the supply currents, calculating the total dissipation and then subtracting the dissipation in the load and feedback network.
15V I 37.5mA
resistance between the layer is small. Copper board stiffeners and plated through holes can also be used to spread the heat generated by the device. Table 1 lists thermal resistance for several different board sizes and copper areas. All measurements were taken in still air on 3/32" FR-4 board with 2oz copper. This data can be used as a rough guideline in estimating thermal resistance. The thermal resistance for each application will be affected by thermal interactions with other components as well as board size and shape.
Table 1. Fused 16-Lead SO Package
COPPER AREA (2oz) TOPSIDE BACKSIDE 2500 sq. mm 2500 sq. mm 1000 sq. mm 2500 sq. mm 600 sq. mm 180 sq. mm 180 sq. mm 180 sq. mm 180 sq. mm 180 sq. mm 180 sq. mm 2500 sq. mm 2500 sq. mm 1000 sq. mm 600 sq. mm 300 sq. mm 100 sq. mm 0 sq. mm
70
TOTAL THERMAL RESISTANCE COPPER AREA (JUNCTION-TO-AMBIENT) 5000 sq. mm 3500 sq. mm 3100 sq. mm 2680 sq. mm 1180 sq. mm 780 sq. mm 480 sq. mm 280 sq. mm 180 sq. mm 40C/W 46C/W 48C/W 49C/W 56C/W 58C/W 59C/W 60C/W 61C/W
THERMAL RESISTANCE (C/W)
60 50 40 30 20 10 0 0 1000 3000 4000 2000 COPPER AREA (mm2) 5000
Figure 7. Thermal Resistance vs Total Copper Area (Top + Bottom)
Calculating Junction Temperature The junction temperature can be calculated from the equation: TJ = (PD)(JA) + TA
12
W
U
UO
+
330
-
1/2 LT1207 SHDN 0.01F 1k -15V 1k 200pF f = 2MHz
12V -12V
LT1206 * F07
Figure 8. Thermal Calculation Example
The dissipation for each amplifier is: PD = (37.5mA)(30V) - (12V)2/(1k||1k) = 0.837W The total dissipation is PD = 1.674W. When a 2500 sq mm PC board with 2oz copper on top and bottom is used, the thermal resistance is 40C/W. The junction temperature TJ is: TJ = (1.674W)(40C/W) + 70C = 137C The maximum junction temperature for the LT1207 is 150C, so the heat sinking capability of the board is adequate for the application. If the copper area on the PC board is reduced to 280mm2 the thermal resistance increases to 60C/W and the junction temperature becomes: TJ = (1.674W)(60C/W) + 70C = 170C Which is above the maximum junction temperature indicating that the heat sinking capability of the board is inadequate and should be increased.
LT1207 * F07
LT1207
TYPICAL APPLICATIO S
Gain of Eleven High Current Amplifier
VIN
OUTPUT OFFSET: < 500V SLEW RATE: 2V/s BANDWIDTH: 4MHz STABLE WITH CL < 10nF
-15V
-15V 560 909
LT1207 * TA03
560
100
RL = 32 VO = 5VRMS THD + NOISE = 0.0009% AT 1kHz = 0.004% AT 20kHz SMALL-SIGNAL 0.1dB BANDWIDTH = 600kHz
+
68pF
+
U
+ -
LT1097
+ -
500pF 330
1/2 LT1207 COMP SHDN 0.01F 3k OUT
10k
LT1207 * TA02
1k
Gain of Ten Buffered Line Driver
15V 1F
15V 1F
+
LT1115
+ +
1F
+
1/2 LT1207 SHDN OUTPUT 0.01F RL
-
-
1F
13
LT1207
TYPICAL APPLICATIO S
CMOS Logic to Shutdown Interface
15V
+ -
5V 10k 2N3904 1/2 LT1207 SHDN 24k
LT1207 * TA04
-15V
Buffer AV = 1
VIN
+ -
1/2 LT1207 COMP SHDN 0.01F* VOUT *OPTIONAL, USE WITH CAPACITIVE LOADS **VALUE OF RF DEPENDS ON SUPPLY VOLTAGE AND LOADING. SELECT FROM TYPICAL AC PERFORMANCE TABLE OR DETERMINE EMPIRICALLY
RF**
LT1207 * TA06
Differential Input--Differential Output Power Amplifier (AV = 4)
+
+
1/2 LT1207
-
1k VIN VOUT 1k
1k
-
1/2 LT1207
-
+
LT1207 * TA08
14
U
Distribution Amplifier
VIN 75
+ -
1/2 LT1207 SHDN RF
75
75 CABLE
75 75
LT1207 * TA05
RG 75
Differential Output Driver
VIN
+
1/2 LT1207
+
-
1k 500 1k 1k
0.01F
VOUT
-
1/2 LT1207
-
+
0.01F
+
LT1207 * TA07
-
LT1207
TYPICAL APPLICATIO S
Paralleling Both CFAs for Guaranteed 500mA Output Drive Current
PACKAGE DESCRIPTIO
0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0 - 8 TYP
0.016 - 0.050 0.406 - 1.270 *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of circuits as described herein will not infringe on existing patent rights.
U
U
VIN
+
1/2 LT1207
3
VOUT
-
1k 1k
+
1/2 LT1207
3
-
1k
LT1207 * TA09
1k
Dimensions in inches (millimeters) unless otherwise noted.
S Package 16-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.386 - 0.394* (9.804 - 10.008) 16 15 14 13 12 11 10 9
0.228 - 0.244 (5.791 - 6.197)
0.150 - 0.157** (3.810 - 3.988)
1 0.053 - 0.069 (1.346 - 1.752)
2
3
4
5
6
7
8
0.004 - 0.010 (0.101 - 0.254)
0.014 - 0.019 (0.355 - 0.483)
0.050 (1.270) TYP
S16 0695
15
LT1207
TYPICAL APPLICATION
CCD Clock Driver. Two 3rd Order Gaussian Filters Produce Clean CCD Clock Signals
45pF CCD ARRAY LOAD 20V CLOCK INPUT 1k CLK 74HC74 D Q Q 100pF 91pF 1k 1k
CLOCK 5 INPUT 0
15 DRIVER OUTPUT 0 510
RELATED PARTS
PART NUMBER LT1206 DESCRIPTION Single 250mA/60MHz Current Feedback Amplifier COMMENTS Single Version of LT1207, 900V/s Slew Rate, 0.02% Differential Gain, 0.17 Differential Phase, with AV = 2 and RL = 30, Stable with CL = 10,000pF, Shutdown Control Reduces Supply Current to 200A Higher Output Current Version of LT1206 Low Cost CFA for Video Applications, 1000V/s Slew Rate, 30mA Output Drive Current, 0.04% Differential Gain, 0.1 Differential Phase, with AV = 2 and RL = 150, 9.5mA Max Supply Current per Op Amp, 2V to 15V Supply Range Fast Settling Voltage Feedback Amplifier, 60ns Settling Time to 0.1%, 10V Step, 5mA Max Supply Current per Op Amp, 9nVHz Input Noise Voltage, Drives All Capacitive Loads, 1mV Max VOS, 0.2% Differential Gain, 0.3 Differential Phase with AV = 2 and RL = 150
LT1210 LT1229/LT1230
Single 1A/30MHz Current Feedback Amplifier Dual/Quad 100MHz Current Feedback Amplifiers
LT1360/LT1361/LT1362
Single/Dual/Quad 50MHz, 800V/s, C-LoadTM Op Amps
C-Load is a trademark of Linear Technology Corporation
16
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977
U
+
1/2 LT1207
10 3300pF 1k 0.01F
-
510
45pF
1k
1k 100pF
1k 91pF
+
1/2 LT1207
10 3300pF -10V 1k
LT1207 * TA10
-
0.01F
LT/GP 0196 10K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 1996

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