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19-0461; Rev 2; 4/97
K ION UAT VAL ILABLE E AVA
IT
400MHz, Ultra-Low-Distortion Op Amps
____________________________Features
o High Speed: 400MHz Unity-Gain Bandwidth (MAX4108) 225MHz -3dB Bandwidth (AVCL = +2, MAX4109) 220MHz -3dB Bandwidth (AVCL = +5, MAX4308) 200MHz -3dB Bandwidth (AVCL = +10, MAX4309) o 1200V/s Slew Rate o Excellent Spurious-Free Dynamic Range: -93dBc at fC = 5MHz (MAX4108) -90dBc at fC = 5MHz (MAX4109) o 100MHz 0.1dB Gain Flatness (MAX4108) o High Full-Power Bandwidth: 300MHz (MAX4108, VO = 2Vp-p) o High Output Drive: 90mA o Output Short-Circuit Protected o Low Differential Gain/Phase: 0.004%/0.008
_______________General Description
The MAX4108/MAX4109/MAX4308/MAX4309 op amps combine ultra-high-speed performance with ultra-lowdistortion operation. The MAX4108 is compensated for unity-gain stability; the MAX4109, MAX4308, and MAX4309 are compensated for minimum closed-loop gains (AVCL) of 2V/V, 5V/V, and 10V/V, respectively. The MAX4108 delivers a 400MHz unity-gain bandwidth with a 1200V/s slew rate. An ultra-low-distortion design provides an unprecedented spurious-free dynamic range of -93dBc (MAX4108) at 5MHz (VOUT = 2Vp-p, RL = 100), making these amplifiers ideal for high-performance RF signal processing. These high-speed op amps feature a wide output voltage swing and a high-current output-drive capability of 90mA.
MAX4108/MAX4109/MAX4308/MAX4309
________________________Applications
High-Speed ADC/DAC Preamp RGB and Composite Video High-Performance Receivers Pulse/RF Amplifier Active Filters Ultrasound Broadcast and High-Definition TV
______________Ordering Information
PART MAX4108ESA MAX4109ESA MAX4308ESA MAX4309ESA TEMP. RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C PIN-PACKAGE 8 SO 8 SO 8 SO 8 SO
________Typical Application Circuit
300 300
__________________Pin Configuration
TOP VIEW
53.6* 10 N.C. 1 12-BIT ADC IN- 2 IN+ 3 60* 300 * USED TO MATCH A 50 SOURCE IMPEDANCE VEE 4 8 VCC VCC OUT VEE
MAX4109
300
MAX4108 MAX4109 MAX4308 MAX4309
7 6 5
SO
DIFFERENCE AMPLIFIER/ADC PREAMPLIFIER ________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
400MHz, Ultra-Low-Distortion Op Amps MAX4108/MAX4109/MAX4308/MAX4309
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VCC to VEE) ..................................................12V Voltage on Any Pin to Ground or Any Other Pin ..............................(VEE - 0.3V) to (VCC + 0.3V) Short-Circuit Duration (OUT to GND) .........................Continuous Continuous Power Dissipation (TA = +70C) SO (derate 5.88mW/C above +70C) ........................471mW Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Junction Temperature ......................................................+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.
ELECTRICAL CHARACTERISTICS
(VCC = +5V, VEE = -5V, TA = TMIN to TMAX, typical values are at TA = +25C, unless otherwise noted.) PARAMETER DC SPECIFICATIONS (RL = ) Input Offset Voltage Input Offset Voltage Drift Input Bias Current Input Offset Current Common-Mode Input Resistance Common-Mode Input Capacitance Input Voltage Noise Integrated Voltage Noise Input Current Noise Integrated Current Noise Common-Mode Input Voltage Common-Mode Rejection Power-Supply Rejection Open-Loop Voltage Gain Quiescent Supply Current VOS TCVOS IB IOS RINCM CINCM en EnRMS in In VCM CMR PSR AOL IS VCM = 2.5V VS = 4.5V to 5.5V VOUT = 2.0V, VCM = 0V, RL = 100 VIN = 0V RL = Output Voltage Swing VOUT RL = 100 Output Current Drive Short-Circuit Output Current AC SPECIFICATIONS (RL = 100) MAX4108 -3dB Bandwidth BW-3dB VOUT 0.1VRMS MAX4109 MAX4308 MAX4309 400 225 220 200 MHz IOUT ISC RL = 33, TA = 0C to +85C Short to ground 2.5 to -3.1 2.5 to -3.1 65 VOUT = 0V VOUT = 0V VOUT = 0V, VIN = -VOS VOUT = 0V, VIN = -VOS Either input Either input f = 10kHz fB = 1MHz to 100MHz f = 10kHz fB = 1MHz to 100MHz -2.5 70 70 70 100 90 100 20 2.9 to -3.8 2.7 to -3.7 90 100 27 1 13 12 0.05 1.5 1 6 75 2 25 2.5 34 2.5 8 mV V/C A A M pF nV/Hz VRMS pA/Hz nARMS V dB dB dB mA SYMBOL CONDITIONS MIN TYP MAX UNITS
V
mA mA
2
_______________________________________________________________________________________
400MHz, Ultra-Low-Distortion Op Amps
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +5V, VEE = -5V, TA = TMIN to TMAX, typical values are at TA = +25C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MAX4108 Full-Power Bandwidth FPBW VOUT = 2Vp-p MAX4109 MAX4308 MAX4309 MAX4108, AVCL = +1 0.1dB Gain Flatness BW0.1dB MAX4109, AVCL = +2 MAX4308, AVCL = +5 MAX4309, AVCL = +10 Slew Rate Settling Time SR tS -2V VOUT 2V -1V VOUT 1V To 0.1% To 0.01% -2V VOUT 2V -50mV VOUT 50mV MIN TYP 300 200 190 130 100 25 100 30 1200 8 12 3 ns 2 0.004 0.008 2 f = 10MHz MAX4108, VOUT = 2Vp-p, AVCL = +1 fC = 5MHz, RL = 100 fC = 20MHz, RL = 100 fC = 5MHz, RL = 100 fC = 20MHz, RL = 100 fC = 5MHz, RL = 100 fC = 20MHz, RL = 100 fC = 5MHz, RL = 100 fC = 20MHz, RL = 100 MAX4108 Third-Order Intercept IP3 fC = 10MHz MAX4109 MAX4308 MAX4309 1 -93 -81 -90 -80 dBc -83 -80 -83 -80 39 36 46 43 3 dBm % degrees pF V/s ns MHz MHz MAX UNITS
MAX4108/MAX4109/MAX4308/MAX4309
AC SPECIFICATIONS (RL = 100) (continued)
Rise/Fall Times
tR, tF
10% to 90%
Differential Gain Differential Phase Input Capacitance Output Resistance
DG DP CIN ROUT
f = 3.58MHz, RL = 150 f = 3.58MHz, RL = 150
MAX4109, VOUT = 2Vp-p, AVCL = +2 Spurious-Free Dynamic Range SFDR MAX4308, VOUT = 2Vp-p, AVCL = +5
MAX4309, VOUT = 2Vp-p, AVCL = +10
_______________________________________________________________________________________
400MHz, Ultra-Low-Distortion Op Amps MAX4108/MAX4109/MAX4308/MAX4309
__________________________________________Typical Operating Characteristics
(VCC = +5V, VEE = -5V, RL = 100, TA = +25C, unless otherwise noted.)
MAX4108 SMALL-SIGNAL GAIN vs. FREQUENCY
MAX4108/9-A
MAX4108 LARGE-SIGNAL GAIN vs. FREQUENCY
MAX4108/9-B
MAX4109 SMALL-SIGNAL GAIN vs. FREQUENCY
1 0 NORMALIZED GAIN (dB) -1 -2 -3 -4 -5 -6 -7 -8 AVCL = +5 VOUT 100mVp-p AVCL = +2
MAX4108/9-C
2 1 0 NORMALIZED GAIN (dB) -1 AVCL = +2 VOUT 100mVp-p AVCL = +1
4 3 2 1 GAIN (dB) 0 -1 -2 -3 -4 -5 -6 VOUT = 2Vp-p AVCL = +1
2
-2 -3 -4 -5 -6 -7 -8 0.1 1
10 FREQUENCY (MHz)
100
1000
0.1
1
10 FREQUENCY (MHz)
100
1000
0.1
1
10 FREQUENCY (MHz)
100
1000
MAX4109 LARGE-SIGNAL GAIN vs. FREQUENCY
1 0 NORMALIZED GAIN (dB) NORMALIZED GAIN (dB) -1 -2 -3 -4 -5 -6 -7 -8 1 10 100 1000 FREQUENCY (MHz) VOUT = 2Vp-p AVCL = +2
MAX4108/9-D
MAX4308 SMALL-SIGNAL GAIN vs. FREQUENCY
MAX4308/9 TOCE
MAX4309 SMALL-SIGNAL GAIN vs. FREQUENCY
3 2 NORMALIZED GAIN (dB) 1 0 -1 -2 -3 -4 -5 -6 AVCL = +20 0.1 1 10 FREQUENCY (MHz) 100 1000 AVCL = +10 VOUT 100mVp-p
MAX4308/9 TOCF
2
4 3 2 1 0 -1 -2 -3 -4 -5 -6 0.1 1 10 FREQUENCY (MHz) 100 VOUT 100mVp-p AVCL = +5
4
1000
MAX4308/MAX4309 LARGE-SIGNAL GAIN vs. FREQUENCY
MAX4308/9 TOCG
MAX4108 HARMONIC DISTORTION vs. FREQUENCY
MAX4108/9-H
MAX4109 HARMONIC DISTORTION vs. FREQUENCY
VOUT = 2Vp-p AVCL = +2
MAX4108/9-i
4 3 2 NORMALIZED GAIN (dB) 1 0 -1 -2 -3 -4 -5 -6 0.1 1 10 FREQUENCY (MHz) 100 MAX4309 AVCL = +10 VOUT = 2Vp-p MAX4308 AVCL = +5
-40 -50 HARMONIC DISTORTION (dBc) -60 -70 -80 -90 -100 -110 2ND HARMONIC VOUT = 2Vp-p AVCL = +1
10 -10 -30 -50 -70 2ND HARMONIC -90 3RD HARMONIC 0.1 1 10
3RD HARMONIC -110 0.1 1 10 100 FREQUENCY (MHz) 100
1000
HARMONIC DISTORTION (dBc)
FREQUENCY (MHz)
4
_______________________________________________________________________________________
400MHz, Ultra-Low-Distortion Op Amps
____________________________Typical Operating Characteristics (continued)
(VCC = +5V, VEE = -5V, RL = 100, TA = +25C, unless otherwise noted.)
MAX4308/MAX4309 HARMONIC DISTORTION vs.FREQUENCY
MAX4108/09 TOCJ
MAX4108/MAX4109/MAX4308/MAX4309
MAX4108 HARMONIC DISTORTION vs. LOAD
MAX4108/9-K
MAX4109 HARMONIC DISTORTION vs. LOAD
AVCL = +2 VOUT = 2Vp-p fO = 20MHz
MAX4108/9-L
-20 -30 HARMONIC DISTORTION (dBc) -40 -50 -60 -70 -80 -90 -100 0.1
HARMONIC DISTORTION (dBc)
-50 -60 -70 -80 -90 -100 3RD HARMONIC 10 100 RESISTIVE LOAD () 1000 2ND HARMONIC
HARMONIC DISTORTION (dBc)
VOUT = 2Vp-p MAX4308: AVCL = +5 MAX4309: AVCL = +10
-30 -40
AVCL = +1 VOUT = 2Vp-p fO = 20MHz
-30 -40 -50 -60 -70 -80 -90 -100 10
2ND HARMONIC
2ND HARMONIC 3RD HARMONIC 1 10 100
3RD HARMONIC
100 RESISTIVE LOAD ()
1000
FREQUENCY (MHz)
MAX4308/MAX4309 HARMONIC DISTORTION vs. LOAD
MAX4108/09 TOCM
MAX4108 HARMONIC DISTORTION vs. OUTPUT SWING
MAX4108/9-N
MAX4109 HARMONIC DISTORTION vs. OUTPUT SWING
AVCL = +2 VOUT = 2Vp-p fO = 20MHz
MAX4108/9-O
-20 -30 HARMONIC DISTORTION (dBc) -40 -50 -60 -70 -80 -90 -100 10 100 RESISTIVE LOAD () 3RD HARMONIC 2ND HARMONIC VOUT = 2Vp-p fO = 5MHz MAX4308: AVCL = +5 MAX4309: AVCL = +10
-30 -40 -50 -60 -70 -80 -90
HARMONIC DISTORTION (dBc)
HARMONIC DISTORTION (dBc)
AVCL = +1 VOUT = 2Vp-p fO = 20MHz
-30 -40 -50 -60 -70 -80 -90
2ND HARMONIC 3RD HARMONIC
2ND HARMONIC 3RD HARMONIC 0.1 1 OUTPUT SWING (Vp-p) 10
-100 1000 0.1 1 OUTPUT SWING (Vp-p) 10
-100
MAX4308/MAX4309 HARMONIC DISTORTION vs. OUTPUT SWING
-30 HARMONIC DISTORTION (dBc) -40 -50 -60 -70 -80 -90 -100 0.1 1 RESISTIVE LOAD () 10 3RD HARMONIC 2ND HARMONIC VOUT = 2Vp-p fO = 5MHz MAX4308: AVCL = +5 MAX4309: AVCL = +10
MAX4108/09 TOCP
MAX4109 TWO-TONE THIRD-ORDER INTERCEPT vs. FREQUENCY
MAX4108/9-Q
INPUT VOLTAGE NOISE vs. FREQUENCY
MAX4108/9-TOCR
-20
45 THIRD-ORDER INTERCEPT (dBm) 40 35 30 25 20 15 10 1 10 FREQUENCY (MHz)
100
VOLTAGE NOISE (nVHz)
10
1 100 1 10 100 1k 10k 100k 1M FREQUENCY (Hz)
_______________________________________________________________________________________
5
400MHz, Ultra-Low-Distortion Op Amps MAX4108/MAX4109/MAX4308/MAX4309
____________________________Typical Operating Characteristics (continued)
(VCC = +5V, VEE = -5V, RL = 100, TA = +25C, unless otherwise noted.)
MAX4108 DIFFERENTIAL GAIN AND PHASE (RL = 150)
MAX4108/9-S
MAX4108 DIFFERENTIAL GAIN AND PHASE (RL = 75)
MAX4108/9-T
MAX4109 DIFFERENTIAL GAIN AND PHASE (RL = 150)
DIFF GAIN (%) 0.004 AVCL = +2V 0.002 0.000 -0.002 -0.004 0 IRE DIFF PHASE (deg) 0.002 AVCL = +2V 0.000 -0.002 -0.004 -0.006 0 IRE 100 100
MAX4108/9-U
DIFF GAIN (%)
DIFF GAIN (%)
0.004 AVCL = +1V 0.002 0.000 -0.002 -0.004 0 IRE 100
0.008 AVCL = +1V 0.006 0.004 0.002 0.000 -0.002 0 IRE 100
DIFF PHASE (deg)
0.004 AVCL = +1V 0.002 0.000 -0.002 -0.004 0 IRE 100
DIFF PHASE (deg)
0.006 AVCL = +1V 0.004 0.002 0.000 -0.002 0 IRE 100
MAX4109 DIFFERENTIAL GAIN AND PHASE (RL = 75)
MAX4108/9-V
MAX4308 DIFFERENTIAL GAIN AND PHASE (RL = 150)
MAX4108/9-W
MAX4309 DIFFERENTIAL GAIN AND PHASE (RL = 150)
DIFF GAIN (%) 0.004 AVCL = +10V 0.002 0.000 -0.002 -0.004 0 IRE DIFF PHASE (deg) 0.002 AVCL = +10V 0.000 -0.002 -0.004 -0.006 -0.008 -0.010 0 IRE 100 100
MAX4108/9-X
DIFF GAIN (%)
DIFF GAIN (%)
0.006 0.004 0.002 0.000 -0.002
AVCL = +2V
0.002 AVCL = +5V 0.000 -0.002 -0.004 -0.006 0 IRE 100
0 IRE DIFF PHASE (deg) 0.006 AVCL = +2V 0.004 0.002 0.000 -0.002 0 IRE
100 DIFF PHASE (deg) 100
0.004 AVCL = +5V 0.002 0.000 -0.002 -0.004 0 IRE 100
MAX4108 SMALL-SIGNAL PULSE RESPONSE (AVCL = +1)
MAX4108/9-Y
MAX4108 SMALL-SIGNAL PULSE RESPONSE (AVCL = +2)
MAX4108/9-Z
MAX4108 LARGE-SIGNAL PULSE RESPONSE (AVCL = +1)
MAX4108/9-AA
IN
GND
IN
GND
IN GND VOLTAGE (500mV/div)
VOLTAGE (20mV/div)
VOLTAGE (10mV/div)
GND OUT GND OUT OUT GND
TIME (10ns/div)
TIME (10ns/div)
TIME (10ns/div)
6
_______________________________________________________________________________________
400MHz, Ultra-Low-Distortion Op Amps
____________________________Typical Operating Characteristics (continued)
(VCC = +5V, VEE = -5V, RL = 100, TA = +25C, unless otherwise noted.)
MAX4108 LARGE-SIGNAL PULSE RESPONSE (AVCL = +2)
MAX4108/9-BB
MAX4108/MAX4109/MAX4308/MAX4309
MAX4109 SMALL-SIGNAL PULSE RESPONSE (AVCL = +2)
MAX4108/9-CC
MAX4109 LARGE-SIGNAL PULSE RESPONSE (AVCL = +2)
MAX4108/9-DD
IN VOLTAGE (500mV/div)
GND
IN
GND
IN
GND
OUT
GND
GND OUT OUT
VOLTAGE (500mV/div)
VOLTAGE (10mV/div)
GND
TIME (10ns/div)
TIME (10ns/div)
TIME (10ns/div)
MAX4308 SMALL-SIGNAL PULSE RESPONSE (AVCL = +5)
MAX4108/9EE
MAX4308 LARGE-SIGNAL PULSE RESPONSE (AVCL = +5)
MAX4108/9FF
MAX4309 SMALL-SIGNAL PULSE RESPONSE (AVCL = +10)
MAX4108/9GG
IN
GND
IN
GND
IN
GND
VOLTAGE (100mV/div)
VOLTAGE (25mV/div)
VOLTAGE (1V/div)
GND
OUT
GND
OUT
GND
OUT
TIME (10ns/div)
TIME (10ns/div)
TIME (10ns/div)
MAX4309 SMALL-SIGNAL PULSE RESPONSE (AVCL = +20)
MAX4108/9HH
MAX4309 LARGE-SIGNAL PULSE RESPONSE (AVCL = +10)
MAX4108/9ii
MAX4309 LARGE-SIGNAL PULSE RESPONSE (AVCL = +20)
MAX4108/9JJ
IN
GND
IN
GND
IN
GND
VOLTAGE (500mV/div)
GND
GND
VOLTAGE (500mV/div)
VOLTAGE (25mV/div)
GND
OUT
OUT
OUT
TIME (10ns/div)
TIME (10ns/div)
TIME (10ns/div)
_______________________________________________________________________________________
7
400MHz, Ultra-Low-Distortion Op Amps MAX4108/MAX4109/MAX4308/MAX4309
____________________________Typical Operating Characteristics (continued)
(VCC = +5V, VEE = -5V, RL = 100, TA = +25C, unless otherwise noted.)
POWER-SUPPLY REJECTION vs. FREQUENCY
MAX4108/9-KK
COMMON-MODE REJECTION vs. FREQUENCY
MAX4108/9-LL
CLOSED-LOOP OUTPUT IMPEDANCE vs. FREQUENCY
MAX4108/9-MM
100 90 POWER-SUPPLY REJECTION (dB) 80 70 60 50 40 30 20 10 0 0.2 1 10 FREQUENCY (MHz) 100 MAX4109/ MAX4309 MAX4108/MAX4308
110 100 COMMON-MODE REJECTION (dB) 90 80 70 60 50 40 30 20 10 MAX4109/ MAX4309 MAX4108/MAX4308
1000
OUTPUT IMPEDANCE () 10 100 1000
100
10
1
0.1 0.1 1 0.1 1 10 FREQUENCY (MHz) 100 1000 FREQUENCY (MHz)
1000
OUTPUT SWING vs. LOAD RESISTANCE
MAX4108/9-NN
INPUT OFFSET VOLTAGE vs. TEMPERATURE
MAX4108/9-OO
INPUT BIAS CURRENT vs. TEMPERATURE
23 21 19 CURRENT (A)
MAX4108/9-PP
4.0 3.5 OUTPUT SWING (VPEAK) 3.0 2.5 2.0 1.5 1.0 0.5 0 10 30 50 70 90 110 130
2.0 1.8 1.6 VOLTAGE (mV) 1.4 1.2 1.0 0.8 0.6 0.4
25
17 15 13 11 9 7 5
150
-75
-50 -25
0
25
50
75
100 125
-75
-50 -25
0
25
50
75
100 125
LOAD RESISTANCE ()
TEMPERATURE (C)
TEMPERATURE (C)
INPUT OFFSET CURRENT vs. TEMPERATURE
MAX4108/9-QQ
POWER-SUPPLY CURRENT vs. TEMPERATURE
MAX4108/9-RR
OUTPUT SWING vs. TEMPERATURE
4.0 3.0 OUTPUT SWING (V) 2.0 1.0 0.0 -1.0 -2.0 -3.0 -4.0 RL = 100 RL = -75 -50 -25 0 25 50 75 100 125 RL = RL = 100
MAX4108/9-SS
0.100
30 POSITIVE SUPPLY CURRENT 20 CURRENT (mA) 10 0 -10
5.0
0.080 CURRENT (A)
0.060
0.040 -20 0.020 -75 -50 -25 0 25 50 75 100 125 TEMPERATURE (C) -30 -75
NEGATIVE SUPPLY CURRENT
-5.0 -50 -25 0 25 50 75 100 125 TEMPERATURE (C) TEMPERATURE (C)
8
_______________________________________________________________________________________
400MHz, Ultra-Low-Distortion Op Amps
_____________________Pin Description
PIN 1 2 3 4, 5 6 7, 8 NAME N.C. ININ+ VEE OUT VCC Inverting Input Noninverting Input Negative Power Supply, connect to -5VDC. Amplifier Output Positive Power Supply, connect to +5VDC. FUNCTION No Connection. Not internally connected.
_______________Detailed Description
Choosing Resistor Values
Unity-Gain Configuration The MAX4108 is internally compensated for unity gain. When configured for unity gain, the device requires a small resistor in series with the feedback path. This resistor improves the AC response by reducing the Q of the tank circuit, which is formed by parasitic feedback inductance and capacitance.
Inverting and Noninverting Configurations The values of the gain-setting feedback and input resistors are important design considerations. Large resistor values will increase voltage noise, and will interact with the amplifier's input and PC board capacitance to generate undesirable poles and zeros, which can decrease bandwidth or cause oscillations. For example, a noninverting gain of +2, using 1k resistors combined with 2pF of input capacitance and 0.5pF of board capacitance, will cause a feedback pole at 128MHz. If this pole is within the anticipated amplifier bandwidth, it will jeopardize stability. Reducing these 1k resistors to 100 will extend the pole frequency to 1.28GHz, but could limit output swing by adding 200 in parallel with the amplifier's load. Clearly, the selection of resistor values must be tailored to the specific application.
The MAX4108/MAX4109/MAX4308/MAX4309 are ultralow-distortion, high-bandwidth op amps. The output distortion will be degraded as the total load resistance seen by the amplifier decreases. To minimize distortion products, keep the input and gain-setting resistors relatively large. A 500 feedback resistor combined with an appropriate input resistor to set the gain will provide excellent AC performance without significantly increasing distortion.
MAX4108/MAX4109/MAX4308/MAX4309
RG
RF
MAX4108 ISOLATION RESISTANCE () 20 MAX4308 15 MAX4109/MAX4309 10
RS VIN CL RL
5 PART MAX4108 MAX4109 MAX4308 MAX4309 RF () 24 500 500 500 RG () 500 125 56 GAIN (V/V) 1 2 5 10
0 10 40 70 100 130 160 190 220 CAPACITANCE (pF)
Figure 1a. Using an Isolation Resistor for High Capacitive Loads
Figure 1b. Optimal Isolation Resistor (RS) vs. Capacitive Load
_______________________________________________________________________________________
MAX4108/9-1B
25
9
400MHz, Ultra-Low-Distortion Op Amps MAX4108/MAX4109/MAX4308/MAX4309
Driving Capacitive Loads
The MAX4108/MAX4109/MAX4308/MAX4309 are optimized for AC performance. They are not designed to drive highly reactive loads. Reactive loads will decrease phase margin and may produce excessive ringing and oscillation. Figure 1a shows a circuit that eliminates this problem, and Figure 1b is a graph of the optimal isolation resistor (R S ) vs. capacitive load. Figures 2a-2d show how a capacitive load causes excessive peaking of the amplifier's bandwidth if the capacitive load is not isolated (RS) from the amplifier. A small isolation resistor (usually 15 to 22) placed
MAX4108/9-2A
10 CLOSED-LOOP GAIN (dB) 8 6 4 2 0 -2 -4 -6 -8
RS = 0 AVCL = +1
CL = 15pF
18 CLOSED-LOOP GAIN (dB) 16 14 12 10 8 6 4 2 0
RS = 0 AVCL = +2
CL = 15pF
CL = 10pF
CL = 10pF
CL = 5pF
CL = 5pF
0.1
1
10 FREQUENCY (MHz)
100
1000
0.1
1
10 FREQUENCY (MHz)
100
1000
Figure 2a. MAX4108 Response vs. Capacitive Load--No Resistive (RS) Isolation (circuit shown in Figure 1a)
Figure 2b. MAX4109 Response vs. Capacitive Load--No Resistive (RS) Isolation (circuit shown in Figure 1a)
MAX4108/9-2C
3 2 NORMALIZED GAIN (dB) 1 0 -1 -2 -3 -4 -5 -6 0.1
RS = 0 AVCL = +5 CL = 15pF
3 2 NORMALIZED GAIN (dB) 1 0 -1 -2 -3 -4
RS = 0 AVCL = +10 CL = 15pF
CL = 5pF CL = 10pF
CL = 10pF CL = 5pF 1 10 FREQUENCY (MHz) 100 1000
-5 -6 0.1 1 10 FREQUENCY (MHz) 100 1000
Figure 2c. MAX4308 Response vs. Capacitive Load--No Resistive (RS) Isolation (circuit shown in Figure 1a)
10
Figure 2d. MAX4309 Response vs. Capacitive Load--No Resistive (RS) Isolation (circuit shown in Figure 1a)
______________________________________________________________________________________
MAX4108/9-2D
4
4
MAX4108/9-2B
12
20
400MHz, Ultra-Low-Distortion Op Amps
before the reactive load prevents ringing and oscillation. At higher capacitive loads, AC performance will be controlled by the interaction of the load capacitance and isolation resistor. Figures 3a-3c show the effect of an isolation resistor on the MAX4108/MAX4109/ MAX4308/MAX4309 closed-loop response. Coaxial cable and other transmission lines are easily driven when terminated at both ends with their characteristic impedance. When driving back-terminated transmission lines, the capacitance of the transmission line is essentially eliminated.
CLOSED-LOOP GAIN (dB)
MAX4108/MAX4109/MAX4308/MAX4309
10 9 8 7 6 5 4 3 2 1 0.1
CL = 10pF AVCL = +2
RS = 8.2
ADC Input Buffers
Input buffer amplifiers can be a source of significant errors in high-speed ADC applications. The input buffer is usually required to rapidly charge and discharge the ADC's input, which is often capacitive (see the section Driving Capacitive Loads). In addition, a high-speed ADC's input impedance often changes very rapidly during the conversion cycle, requiring 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 a low and stable distortion over load makes the MAX4108/MAX4109/ MAX4308/MAX4309 ideally suited for use as buffer amplifiers in high-speed ADC applications.
RS = 15
1
10 FREQUENCY (MHz)
100
1000
Figure 3b. MAX4308 Response vs. Capacitive Load with Resistive (RS) Isolation (circuit shown in Figure 1a)
MAX4108/9-3A
10 CLOSED-LOOP GAIN (dB) 8 6 4 2 0 -2 -4 -6 -8 0.1
CL = 10pF AVCL = +1 RS = 10 RS = 22
3 2 NORMALIZED GAIN (dB) 1 0 -1 -2 -3 -4 -5
CL = 10pF AV = +5
RS = 30
RS = 8.2 RS = 15 RS = 47
1
10 FREQUENCY (MHz)
100
1000
-6 0.1 1 10 FREQUENCY (MHz) 100 1000
Figure 3a. MAX4108 Response vs. Capacitive Load with Resistive (RS) Isolation (circuit shown in Figure 1a)
Figure 3c. MAX4108/MAX4309 Response vs. Capacitive Load with Resistive (RS) Isolation (circuit shown in Figure 1a)
______________________________________________________________________________________
MAX4108/9-3C
12
4
MAX4108/9-3B
11
11
400MHz, Ultra-Low-Distortion Op Amps MAX4108/MAX4109/MAX4308/MAX4309
___________________Chip Information
TRANSISTOR COUNT: 57 SUBSTRATE CONNECTED TO VEE
________________________________________________________Package Information
SOICN.EPS
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
12 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 (c) 1997 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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