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19-4757; Rev 3; 10/98
ANUAL N KIT M LUATIO ATA SHEET EVA WS D FOLLO
740MHz, Low-Noise, Low-Distortion Op Amps in SOT23-5
Features
o Low 2.1nV/Hz Voltage Noise Density o Ultra-High 740MHz -3dB Bandwidth (MAX4304, AVCL = 2V/V) o 100MHz 0.1dB Gain Flatness (MAX4104/4105) o 1400V/s Slew Rate (MAX4105/4305) o -88dBc SFDR (5MHz, RL = 100) (MAX4104/4304) o High Output Current Drive: 70mA o Low Differential Gain/Phase Error: 0.01%/0.01 (MAX4104/4304) o Low 1mV Input Offset Voltage o Available in Space-Saving 5-Pin SOT23 Package
General Description
The MAX4104/MAX4105/MAX4304/MAX4305 op amps feature ultra-high speed, low noise, and low distortion in a SOT23 package. The unity-gain-stable MAX4104 requires only 20mA of supply current while delivering 625MHz bandwidth and 400V/s slew rate. The MAX4304, compensated for gains of +2V/V or greater, delivers a 730MHz bandwidth and a 1000V/s slew rate. The MAX4105 is compensated for a minimum gain of +5V/V and delivers a 410MHz bandwidth and a 1400V/sec slew rate. The MAX4305 has +10V/V minimum gain compensation and delivers a 340MHz bandwidth and a 1400V/s slew rate. Low voltage noise density of 2.1nV/Hz and -88dBc spurious-free dynamic range make these devices ideal for low-noise/low-distortion video and telecommunications applications. These op amps also feature a wide output voltage swing of 3.7V and 70mA output currentdrive capability. For space-critical applications, they are available in a miniature 5-pin SOT23 package.
MAX4104/MAX4105/MAX4304/MAX4305
Selector Guide
PART MINIMUM BANDWIDTH STABLE (MHz) GAIN (V/V) 1 2 5 10 625 740 410 340 PIN-PACKAGE 5-pin SOT23, 8-pin SO 5-pin SOT23, 8-pin SO 5-pin SOT23, 8-pin SO 5-pin SOT23, 8-pin SO
________________________Applications
Video ADC Preamp Pulse/RF Telecom Applications Video Buffers and Cable Drivers Ultrasound Active Filters ADC Input Buffers
MAX4104 MAX4304 MAX4105 MAX4305
Ordering Information
PART MAX4104ESA TEMP. RANGE -40C to +85C PINPACKAGE 8 SO 5 SOT23-5 SOT TOP MARK -- ACCO
Typical Application Circuit
MAX4104EUK-T -40C to +85C
Ordering Information continued at end of data sheet.
Pin Configurations
INPUT 8 to 16-BIT HIGH-SPEED ADC
TOP VIEW
OUT 1 5 VCC
MAX4304
VEE 2 330 330 IN+ 3 4 IN-
MAX4104 MAX4105 MAX4304 MAX4305
SOT23-5
ADC BUFFER WITH GAIN (AVCL = 2V/V)
Pin Configurations continued at end of data sheet.
1
________________________________________________________________ Maxim Integrated Products
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740MHz, Low-Noise, Low-Distortion Op Amps in SOT23-5 MAX4104/MAX4105/MAX4304/MAX4305
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VCC to VEE)................................................+12V Voltage on Any Pin to Ground..........(VEE - 0.3V) to (VCC + 0.3V) Short-Circuit Duration (VOUT to GND)........................Continuous Continuous Power Dissipation (TA = +70C) 5-pin SOT23 (derate 7.1mW/C above +70C)...........571mW 8-pin SO (derate 5.9mW/C above +70C).................471mW Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10sec) .............................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
DC ELECTRICAL CHARACTERISTICS
(VCC = +5V, VEE = -5V, VCM = 0, RL = 100k, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER Operating Supply Voltage Range Input Offset Voltage Input Offset-Voltage Drift Input Bias Current Input Offset Current Differential Input Resistance Common-Mode Input Resistance Input Common-Mode Voltage Range Common-Mode Rejection Ratio Positive Power-Supply Rejection Ratio Negative Power-Supply Rejection Ratio Quiescent Supply Current Open-Loop Gain Output Voltage Swing Output Current Drive Short-Circuit Output Current Open-Loop Output Impedance SYMBOL VCC/VEE VOS TCVOS IB IOS RIN RIN VCM CMRR PSSR+ PSRRIS AVOL VOUT IOUT ISC ZOUT -0.8V VIN 0.8V Either input Guaranteed by CMRR test -2.8V VCM 4.1V VCC = 3.5V to 5.5V VEE = -3.5V to -5.5V VOUT = 0 -2.8V VOUT 2.8V, RL = 100 RL = 100k RL = 100 RL = 30 RL = short to ground 55 -2.8 80 75 55 95 85 65 20 65 3.5 -3.7 to +3.8 3.0 -3.5 to +3.4 53 70 80 9 27 CONDITIONS Guaranteed by PSRR test VOUT = 0 MAX4_0_ESA MAX4_0_EUK MIN 3.5 TYP 5 1 1 2.5 32 0.5 6 1.5 +4.1 70 5.0 MAX 5.5 6 8 UNITS V mV V/C A A k M V dB dB dB mA dB V mA mA
2
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740MHz, Low-Noise, Low-Distortion Op Amps in SOT23-5
AC ELECTRICAL CHARACTERISTICS
(VCC = +5V, VEE = -5V, VCM = 0, RL = 100; AV = +1V/V for MAX4104, +2V/V for MAX4304, +5V/V for MAX4105, +10V/V for MAX4305; TA = +25C; unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MAX4104 -3dB Bandwidth BW(-3dB) VOUT = 100mVp-p MAX4304 MAX4105 MAX4305 MAX4104 0.1dB Bandwidth BW(0.1) VOUT = 100mVp-p MAX4304 MAX4105 MAX4305 MAX4104 Full-Power Bandwidth FPBW VOUT = 2Vp-p MAX4304 MAX4105 MAX4305 MAX4104 Slew Rate SR VOUT = 2Vp-p MAX4304 MAX4105 MAX4305 Settling Time to 0.1% tS VOUT = 2Vp-p MAX4104/ MAX4304 SFDR VOUT = 2Vp-p MAX4105/ MAX4305 to 0.1% to 0.01% fC = 5MHz fC = 20MHz fC = 5MHz fC = 20MHz MIN TYP 625 740 410 340 100 60 80 70 115 285 370 320 400 1000 1400 1400 20 25 -88 -67 -74 -61 0.01 0.02 0.01 0.02 2.1 3.1 1 % degrees nV/Hz pA/Hz dBc ns V/s MHz MHz MHz MAX UNITS
MAX4104/MAX4105/MAX4304/MAX4305
Spurious-Free Dynamic Range
Differential Gain Error Differential Phase Error Input Voltage Noise Density Input Current Noise Density Output Impedance
DG DP en in ZOUT
NTSC, RL = 150 NTSC, RL = 150 f = 1MHz f = 1MHz f = 10MHz
MAX4104/MAX4304 MAX4105/MAX4305 MAX4104/MAX4304 MAX4105/MAX4305
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3
740MHz, Low-Noise, Low-Distortion Op Amps in SOT23-5 MAX4104/MAX4105/MAX4304/MAX4305
__________________________________________Typical Operating Characteristics
(VCC = +5V, VEE = -5V, RF = 330, RL = 100, TA = +25C, unless otherwise noted.)
MAX4104 SMALL-SIGNAL GAIN vs. FREQUENCY (AVCL = +1)
MAX4104 TOC01
MAX4304 SMALL-SIGNAL GAIN vs. FREQUENCY (AVCL = +2)
MAX4104 TOC 2
MAX4105 SMALL-SIGNAL GAIN vs. FREQUENCY (AVCL = +5)
4 3 NORMALIZED GAIN (dB) 2 1 0 -1 -2 -3 -4 -5 VOUT = 100mVp-p
MAX4104 TOC 3
5 4 3 2 GAIN (dB) 1 0 -1 -2 -3 -4 -5 100k 1M 10M FREQUENCY (Hz) 100M VOUT = 100mVp-p
5 4 3 NORMALIZED GAIN (dB) 2 1 0 -1 -2 -3 -4 -5 VOUT = 100mVp-p
5
1G
100k
1M
10M FREQUENCY (Hz)
100M
1G
100k
1M
10M FREQUENCY (Hz)
100M
1G
MAX4305 SMALL-SIGNAL GAIN vs. FREQUENCY (AVCL = +10)
MAX4104 TOC 4
MAX4104 GAIN FLATNESS vs. FREQUENCY (AVCL = +1)
MAX4104 TOC 5
MAX4304 GAIN FLATNESS vs. FREQUENCY (AVCL = +2)
0.4 0.3 NORMALIZED GAIN (dB) 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 VOUT = 100mVp-p
MAX4104 TOC 6
5 4 3 NORMALIZED GAIN (dB) 2 0 -1 -2 -3 -4 -5
VOUT = 100mVp-p
0.5 0.4 0.3 0.2 GAIN (dB) 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 VOUT = 100mVp-p
0.5
1
100k
1M
10M FREQUENCY (Hz)
100M
1G
100k
1M
10M FREQUENCY (Hz)
100M
1G
100k
1M
10M FREQUENCY (Hz)
100M
1G
MAX4105 GAIN FLATNESS vs. FREQUENCY (AVCL = +5)
MAX4104 TOC 7
MAX4305 GAIN FLATNESS vs. FREQUENCY (AVCL = +10)
MAX4104 TOC 8
MAX4104 LARGE-SIGNAL GAIN vs. FREQUENCY (AVCL = +1)
4 3 2 GAIN (dB) 1 0 -1 -2 -3 -4 -5 VOUT = 2Vp-p
MAX4104 TOC9
0.5 0.4 0.3 NORMALIZED GAIN (dB) 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 100k 1M 10M FREQUENCY (Hz) 100M VOUT = 100mVp-p
0.5 0.4 0.3 NORMALIZED GAIN (dB) 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 VOUT = 100mVp-p
5
1G
100k
1M
10M FREQUENCY (Hz)
100M
1G
100k
1M
10M FREQUENCY (Hz)
100M
1G
4
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740MHz, Low-Noise, Low-Distortion Op Amps in SOT23-5
Typical Operating Characteristics (continued)
(VCC = +5V, VEE = -5V, RF = 330, RL = 100, TA = +25C, unless otherwise noted.)
MAX4304 LARGE-SIGNAL GAIN vs. FREQUENCY (AVCL = +2)
MAX4104 TOC10
MAX4104/MAX4105/MAX4304/MAX4305
MAX4105 LARGE-SIGNAL GAIN vs. FREQUENCY (AVCL = +5)
MAX4104 TOC 11
MAX4305 LARGE-SIGNAL GAIN vs. FREQUENCY (AVCL = +10)
4 3 NORMALIZED GAIN (dB) 2 1 0 -1 -2 -3 -4 -5 VOUT = 2Vp-p
MAX4104 TOC12
5 4 3 NORMALIZED GAIN (dB) 2 1 0 -1 -2 -3 -4 -5
VOUT = 2Vp-p
5 4 3 NORMALIZED GAIN (dB) 2 1 0 -1 -2 -3 -4 -5 VOUT = 2Vp-p
5
100k
1M
10M FREQUENCY (Hz)
100M
1G
100k
1M
10M FREQUENCY (Hz)
100M
1G
100k
1M
10M FREQUENCY (Hz)
100M
1G
POSITIVE POWER-SUPPLY REJECTION vs. FREQUENCY
MAX4104 TOCM
NEGATIVE POWER-SUPPLY REJECTION vs. FREQUENCY
MAX4104 TOCN
COMMON-MODE REJECTION vs. FREQUENCY
-10 -20 -30 CMR (dB) -40 -50 -60 -70 -80 -90 -100
MAX4104 TOCO
0 -10 POWER-SUPPLY REJECTION (dB) -20 -30 -40 -50 -60 -70 -80 -90 -100 100k 1M 10M FREQUENCY (Hz) 100M
20 10 POWER-SUPPLY REJECTION (dB) 0 -10 -20 -30 -40 -50 -60 -70 -80
0
1G
100k
1M
10M FREQUENCY (Hz)
100M
1G
10k
100k
1M
10M
100M
1G
FREQUENCY (Hz)
VOLTAGE NOISE DENSITY vs. FREQUENCY (INPUT REFERRED)
MAX4104 TOC-P
CURRENT NOISE DENSITY vs. FREQUENCY (INPUT REFERRED)
MAX4104 TOC-Q
CLOSED-LOOP OUTPUT IMPEDANCE vs. FREQUENCY
MAX4104 TOC-R
100 VOLTAGE NOISE DENSITY (nV/Hz)
100 CURRENT NOISE DENSITY (pA/Hz)
1000
OUTPUT IMPEDANCE ()
100
10
10
10
1
0.1
1 1 10 100 1k 10k 100k FREQUENCY (Hz) 1M 10M
1 1 10 100 1k 10k 100k FREQUENCY (Hz) 1M 10M
0.01 100k 1M 10M FREQUENCY (Hz) 100M 1G
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5
740MHz, Low-Noise, Low-Distortion Op Amps in SOT23-5 MAX4104/MAX4105/MAX4304/MAX4305
Typical Operating Characteristics (continued)
(VCC = +5V, VEE = -5V, RF = 330, RL = 100, TA = +25C, unless otherwise noted.)
MAX4104/MAX4304 DIFFERENTIAL GAIN AND PHASE
MAX4104 TOC-S
MAX4105/MAX4305 DIFFERENTIAL GAIN AND PHASE
MAX4104 TOC T
MAX4104/MAX4304 HARMONIC DISTORTION vs. FREQUENCY
-10 HARMONIC DISTORTION (dBc) -20 -30 -40 -50 -60 -70 -80 -90 -100 3RD HARMONIC 100k 1M 10M 100M 2ND HARMONIC VOUT = 2Vp-p
MAX4104 TOC-U
DIFF GAIN (%)
0.000 -0.005 -0.010 -0.015 0 0.015 0.010 0.005 0.000 -0.005 0 IRE RL = 150 RL = 150
DIFF GAIN (%)
0.005
0.03 0.02 0.01 0.00 -0.01 RL = 150 0 0.025 0.020 0.015 0.010 0.005 0.000 -0.005 0 IRE
0
100 DIFF PHASE (deg)
100 RL = 150
DIFF PHASE (deg)
100
100
FREQUENCY (Hz)
MAX4105/MAX4305 HARMONIC DISTORTION vs. FREQUENCY
MAX4104 TOC-V
MAX4104/MAX4304 HARMONIC DISTORTION vs. LOAD
MAX4104 TOC-W
MAX4105/MAX4305 HARMONIC DISTORTION vs. LOAD
-10 HARMONIC DISTORTION (dBc) -20 -30 -40 -50 -60 -70 -80 -90 -100 3RD HARMONIC 2ND HARMONIC f = 5MHz VOUT = 2Vp-p
MAX4104 TOC-X
0 -10 -20 DISTORTION (dBc) -30 -40 -50 -60 -70 -80 -90 -100 100k 1M 10M 3RD HARMONIC 2ND HARMONIC VOUT = 2Vp-p
0 -10 HARMONIC DISTORTION (dBc) -20 -30 -40 -50 -60 -70 -80 -90 -100 3RD HARMONIC 2ND HARMONIC f = 5MHz VOUT = 2Vp-p
0
100M
0 100 200 300 400 500 600 700 800 900 1k LOAD ()
0 100 200 300 400 500 600 700 800 900 1k LOAD ()
FREQUENCY (Hz)
MAX4104/MAX4304 HARMONIC DISTORTION vs. OUTPUT SWING
MAX4104 TOC-Y
MAX4105/MAX4305 HARMONIC DISTORTION vs. OUTPUT SWING
-10 HARMONIC DISTORTION (dBc) -20 -30 -40 -50 -60 -70 -80 -90 -100 3RD HARMONIC 2ND HARMONIC f = 5MHz
MAX4104 TOC-Z
OUTPUT SWING vs. LOAD RESISTANCE
MAX4104 TOCAA
0 -10 HARMONIC DISTORTION (dBc) -20 -30 -40 -50 -60 -70 -80 -90 -100 0.5 1.0 1.5 2.0 2.5 3.0 3.5 3RD HARMONIC 2ND HARMONIC f = 5MHz
0
8 7 OUTPUT SWING (Vp-p) 6 5 4 3 2 1
4.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0
50
100 150 200 250 300 350 400 LOAD RESISTANCE ()
OUTPUT SWING (Vp-p)
OUTPUT SWING (Vp-p)
6
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740MHz, Low-Noise, Low-Distortion Op Amps in SOT23-5
Typical Operating Characteristics (continued)
(VCC = +5V, VEE = -5V, RF = 330, RL = 100, TA = +25C, unless otherwise noted.)
MAX4104/MAX4105/MAX4304/MAX4305
INPUT OFFSET VOLTAGE vs. TEMPERATURE
3.0 2.5 2.0 1.5 1.0 0.5 0.0 -0.5 -1.0 -1.5 -2.0 -2.5 -3.0 -40 -15 10 35 60 TEMPERATURE (C)
MAX4104 TOCBB
INPUT OFFSET CURRENT vs. TEMPERATURE
MAX4104 TOC-CC
INPUT BIAS CURRENT vs. TEMPERATURE
MAX4104 TOC-DD
4 3 INPUT OFFSET CURRENT (A) 2 1 0 -1 -2 -3
35
INPUT OFFSET VOLTAGE (mV)
INPUT BIAS CURRENT (A)
34
33
32
31
30 -40 -15 10 35 60 85 -40 -15 10 35 60 85 TEMPERATURE (C) TEMPERATURE (C)
85
SUPPLY CURRENT vs. TEMPERATURE
MAX4104 TOC-EE
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX4104 TOC-FF
POSITIVE OUTPUT VOLTAGE SWING vs. TEMPERATURE
3.9 VOLTAGE SWING (V) 3.8 3.7 3.6 3.5 RL = 100k 3.4 3.3 3.2 RL = 100k
MAX4104 TOC-GG
25 24 23 SUPPLY CURRENT (mA) 22 21 20 19 18 17 16 15 -40 -15 10 35 60
25 24 23 SUPPLY CURRENT (mA) 22 21 20 19 18 17 16 15
4.0
85
9.0
9.5
10.0
10.5
11.0
-40
-15
10
35
60
85
TEMPERATURE (C)
SUPPLY VOLTAGE (V)
TEMPERATURE (C)
MAX4104 SMALL-SIGNAL PULSE RESPONSE (AV = +1)
MAX4104 TOCHH
MAX4304 SMALL-SIGNAL PULSE RESPONSE (AV = +2)
MAX4104 TOCII
MAX4105 SMALL-SIGNAL PULSE RESPONSE (AV = +5)
MAX4104 TOCJJ
+50mV IN -50mV GND
+25mV IN -25mV +50mV
IN GND +10mV -10mV GND
+50mV
+50mV OUT -50mV -50mV 10ns/div 10ns/div -50mV 10ns/div GND OUT GND OUT GND
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7
740MHz, Low-Noise, Low-Distortion Op Amps in SOT23-5 MAX4104/MAX4105/MAX4304/MAX4305
Typical Operating Characteristics (continued)
(VCC = +5V, VEE = -5V, RF = 330, RL = 100, TA = +25C, unless otherwise noted.)
MAX4305 SMALL-SIGNAL PULSE RESPONSE (AV = +10)
MAX4104 TOCKK
MAX4104 LARGE-SIGNAL PULSE RESPONSE (AV = +1)
MAX4104 TOCLL
IN +5mV -5mV
GND
+1V IN -1V GND
+50mV +1V OUT GND OUT -1V -50mV 10ns/div 10ns/div GND
MAX4305 LARGE-SIGNAL PULSE RESPONSE (AV = +2)
MAX4104 TOCMM
MAX4105 LARGE-SIGNAL PULSE RESPONSE (AV = +5)
MAX4104 TOCNN
IN +500mV GND -500mV
IN +200mV -200mV
GND
+1V
+1V
OUT
GND
OUT
GND
-1V 10ns/div
-1V 10ns/div
MAX4305 LARGE-SIGNAL PULSE RESPONSE (AV = +10)
MAX4104 TOCOO
IN +100mV -100mV
GND
+1V
OUT
GND
-1V 10ns/div
8
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740MHz, Low-Noise, Low-Distortion Op Amps in SOT23-5
_____________________Pin Description
PIN NAME SOT23-5 SO 1, 5, 8 2 3 4 6 7 N.C. ININ+ VEE OUT VCC Not internally connected. Amplifier Inverting Input Amplifier Noninverting Input Negative Power Supply Amplifier Output Positive Power Supply FUNCTION
Regardless of whether or not a constant-impedance board is used, it is best to observe the following guidelines when designing the board: 1) Do not use wire-wrapped boards (they are much too inductive) or breadboards (they are much too capacitive). 2) Do not use IC sockets. IC sockets increase reactances. 3) Keep signal lines as short and straight as possible. Do not make 90 turns; round all corners. 4) Observe high-frequency bypassing techniques to maintain the amplifier's accuracy and stability. 5) Bear in mind that, in general, surface-mount components have shorter bodies and lower parasitic reactance, resulting in greatly improved high-frequency performance over through-hole components. The bypass capacitors should include 1nF and 0.1F ceramic surface-mount capacitors between each supply pin and the ground plane, located as close to the package as possible. Optionally, place a 10F tantalum capacitor at the power supply pins' point of entry to the PC board to ensure the integrity of incoming supplies. The power-supply trace should lead directly from the tantalum capacitor to the VCC and VEE pins. To minimize parasitic inductance, keep PC traces short and use surface-mount components. Input termination resistors and output back-termination resistors, if used, should be surface-mount types, and should be placed as close to the IC pins as possible.
MAX4104/MAX4105/MAX4304/MAX4305
--
4 3 2 1 5
_______________Detailed Description
The MAX4104/MAX4105/MAX4304/MAX4305 are ultrahigh-speed, low-noise amplifiers featuring -3dB bandwidths up to 880MHz, 0.1dB gain flatness up to 100MHz, and low differential gain and phase errors of 0.01% and 0.01, respectively. These devices operate on dual power supplies ranging from 3.5V to 5.5V and require only 20mA of supply current. The MAX4104/MAX4304/MAX4105/MAX4305 are optimized for minimum closed-loop gains of +1V/V, +2V/V, +5V/V and +10V/V (respectively) with corresponding -3dB bandwidths of 880MHz, 730MHz, 430MHz, and 350MHz. Each device in this family features a low input voltage noise density of only 2.1nV/Hz (at 1MHz), an output current drive of 70mA, and spurious-free dynamic range as low as -88dBc (5MHz, RL = 100).
DC and Noise Errors
The MAX4104/MAX4105/MAX4304/MAX4305 output offset voltage, VOUT (Figure 1), can be calculated with the following equation: VOUT = [VOS + (IB+ x RS) + (IB- x (RF || RG))] [1 + RF / RG] where: VOS = input offset voltage (in volts) 1 + RF/RG = amplifier closed-loop gain (dimensionless) IB+ = noninverting input bias current (in amps) IB- = inverting input bias current (in amps) RG = gain-setting resistor (in ohms) RF = feedback resistor (in ohms) RS = source resistor at noninverting input (in ohms) The following equation represents output noise density:
R en(OUT) = 1 + F RG
___________Applications Information
Layout and Power-Supply Bypassing
The MAX4104/MAX4105/MAX4304/MAX4305 have an extremely high bandwidth, and consequently require careful board layout, including the possible use of constant-impedance microstrip or stripline techniques. To realize the full AC performance of these high-speed amplifiers, pay careful attention to power-supply bypassing and board layout. The PC board should have at least two layers: a signal and power layer on one side, and a large, low-impedance ground plane on the other side. The ground plane should be as free of voids as possible. With multilayer boards, locate the ground plane on a layer that incorporates no signal or power traces.
(i
n x RS
)
2
2 + in x RF || RG + en
(
)
2
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9
740MHz, Low-Noise, Low-Distortion Op Amps in SOT23-5 MAX4104/MAX4105/MAX4304/MAX4305
RG RF RG RF
FB IBOUT VOUT IB+ IN 75 CABLE
INOUT IN+ RT 75 75 CABLE
RS
MAX4104 MAX4105 MAX4304 MAX4305
RT 75
MAX4104 MAX4105 MAX4304 MAX4305
RL 75
Figure 1. Output Offset Voltage
Figure 2. Video Line Driver
where: in = input current noise density (in pA/Hz) en = input voltage noise density (in nV/Hz) The MAX4104/MAX4105/MAX4304/MAX4305 have a very low, 2.1nV/Hz input voltage noise density and 3.1pA/Hz input current noise density. An example of DC-error calculations, using the MAX4304 typical data and the typical operating circuit with RF = RG = 330 (RF || RG = 165) and RS = 50 gives:
VOUT = 32 x 10-6 50 + 32 x 10-6 165 + 1 x 10-3 1 + 1
very rapidly during the conversion cycle--a condition that demands an amplifier with very low output impedance at high frequencies to maintain measurement accuracy. The combination of high-speed, fast slew rate, low noise, and low-distortion available in the MAX4104/MAX4105/MAX4304/MAX4305 makes them ideally suited for use as buffer amplifiers in high-speed ADC applications.
Video Line Driver
The MAX4104/MAX4105/MAX4304/MAX4305 are optimized to drive coaxial transmission lines when the cable is terminated at both ends, as shown in Figure 2. To minimize reflections and maximize power transfer, select the termination resistors to match the characteristic impedance of the transmission line. Cable frequency response can cause variations in the flatness of the signal.
()
(
)
[
]
VOUT = 15.8mV
Calculating total output noise in a similar manner yields the following:
en(OUT) =
Driving Capacitive Loads
2 2 2
[1+ 1]
3.1 x 10-12 x 50 + 3.1 x 10 -12 x 165 + 2.1 x 10 -9
en(OUT) = 4.3nV Hz
With a 200MHz system bandwidth, this calculates to 60.8VRMS (approximately 365Vp-p, using the sixsigma calculation).
ADC Input Buffers
Input buffer amplifiers can be a source of significant error in high-speed ADC applications. The input buffer is usually required to rapidly charge and discharge the ADC's input, which is often capacitive. In addition, the input impedance of a high-speed ADC often changes
10
The MAX4104/MAX4105/MAX4304/MAX4305 provide maximum AC performance when driving no output load capacitance. This is the case when driving a correctly terminated transmission line (i.e., a back-terminated cable). In most amplifier circuits, driving a large load capacitance increases the chance of oscillations occurring. The amplifier's output impedance and the load capacitor combine to add a pole and excess phase to the loop response. If the pole's frequency is low enough and phase margin is degraded sufficiently, oscillations may result. A second concern when driving capacitive loads originates from the amplifier's output impedance, which
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740MHz, Low-Noise, Low-Distortion Op Amps in SOT23-5 MAX4104/MAX4105/MAX4304/MAX4305
30 25 20 15 GAIN (dB) 10 5 0 -5 -10 -15 -20 100k 1M 10M 100M 1G FREQUENCY (Hz) CL = 5pF CL = 10pF CL = 15pF NORMALIZED GAIN (dB) 30 25 20 15 10 5 0 -5 -10 -15 -20 100k 1M 10M 100M 1G FREQUENCY (Hz) CL = 5pF CL = 10pF CL = 15pF
Figure 3a. MAX4104 Frequency Response with Capacitive Load and No Isolation Resistor
Figure 3b. MAX4304 Frequency Response with Capacitive Load and No Isolation Resistor
25 20
25 20 15 NORMALIZED GAIN (dB) 10 5 0 -5 -10 -15 -20 -25 100k 1M 10M 100M 1G FREQUENCY (Hz) CL = 5pF CL = 10pF CL = 15pF NORMALIZED GAIN (dB)
15 10 5 0 -5 -10 -15 -20 -25 100k 1M 10M 100M 1G FREQUENCY (Hz) CL = 5pF CL = 15pF CL = 10pF
Figure 3c. MAX4105 Frequency Response with Capacitive Load and No Isolation Resistor
Figure 3d. MAX4305 Frequency Response with Capacitive Load and No Isolation Resistor
appears inductive at high frequencies. This inductance forms an L-C resonant circuit with the capacitive load, which causes peaking in the frequency response and degrades the amplifier's phase margin. The MAX4104/MAX4105/MAX4304/MAX4305 drive capacitive loads up to 10pF without oscillation. However, some peaking may occur in the frequency domain (Figure 3). To drive larger capacitance loads or to reduce ringing, add an isolation resistor between the amplifier's output and the load (Figure 4). The value of RISO depends on the circuit's gain and the capacitive load (Figure 5). Figure 6 shows the MAX4104/MAX4105/MAX4304/MAX4305 frequency response with the isolation resistor and a capacitive
load. With higher capacitive values, bandwidth is dominated by the RC network formed by RISO and CL; the bandwidth of the amplifier itself is much higher. Also note that the isolation resistor forms a divider that decreases the voltage delivered to the load.
Maxim's High-Speed Evaluation Boards
The MAX4104 evaluation kit manual shows a suggested layout for Maxim's high-speed, single-amplifier evaluation boards. This board was developed using the techniques described previously (see Layout and Power-Supply Bypassing section). The smallest available surface-mount resistors were used for the feedback and back-termination resistors to minimize the
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11
740MHz, Low-Noise, Low-Distortion Op Amps in SOT23-5 MAX4104/MAX4105/MAX4304/MAX4305
4 RG RF 3 2 CL = 47pF CL = 68pF
IN-
MAX4104 MAX4105 MAX4304 MAX4305
OUT RISO
1 GAIN (dB) 0 -1 -2 -3 -4 CL = 83pF
IN+
CL
RL
-5 -6
MAX4104/MAX4304 RISO = 15 100k 1M 10M 100M 1G
FREQUENCY (Hz)
Figure 4. Using an Isolation Resistor (RISO) for High Capacitive Loads
30 OPTIMAL ISLOATION RESISTOR () 25 20 15 10 5 0 0 50 100 150 200 250 CAPACITIVE LOAD (pF) MAX4104/MAX4304 MAX4105/MAX4305
Figure 6. Frequency Responses vs. Capacitive Load with 15 Isolation Resistor
distance from the IC to these resistors, thus reducing the capacitance associated with longer lead lengths. SMA connectors were used for best high-frequency performance. Because distances are extremely short, performance is unaffected by the fact that inputs and outputs do not match a 50 line. However, in applications that require lead lengths greater than 1/4 of the wavelength of the highest frequency of interest, constant-impedance traces should be used. Fully assembled evaluation boards are available for the MAX4104 in an 8-pin SO package.
Ordering Information (continued)
PART MAX4105ESA MAX4105EUK-T MAX4304ESA MAX4304EUK-T MAX4305ESA* MAX4305EUK-T TEMP. RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C PINPACKAGE 8 SO 5 SOT23-5 8 SO 5 SOT23-5 8 SO 5 SOT23-5 SOT TOP MARK -- ACCP -- ACCQ -- ACCR
Figure 5. Optimal Isolation Resistor (RISO) vs. Capacitive Load
Pin Configurations (continued)
TOP VIEW
N.C. 1 IN- 2 IN+ 3 VEE 4
MAX4104 MAX4105
8 7 6
N.C. VCC OUT N.C.
*Future product--contact factory for availability.
Chip Information
TRANSISTOR COUNT: 44 SUBSTRATE CONNECTED TO VEE
MAX4304 MAX4305
SO
5
12
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