Programmable Gain a Instrumentation Amplifier AD625 FUNCTIONAL BLOCK DIAGRAM FEATURES User Programmed Gains of 1 to 10,000 Low Gain Error: 0.02% Max Low Gain TC: 5 ppm/ C Max 50 AD625 INPUT + + Low Nonlinearity: 0.001% Max Low Offset Voltage: 25 V GAIN 10k SENSE SENSE Low Noise 4 nV/Hz (at 1 kHz) RTI GAIN Gain Bandwidth Product: 25 MHz 10k DRIVE 16-Lead Ceramic or Plastic DIP Package, V OUTPUT B 10k + +GAIN 20-Terminal LCC Package DRIVE 10k Standard Military Drawing Available REFERENCE +GAIN MlL-Standard Parts Available SENSE + + 50 Low Cost +INPUT PRODUCT DESCRIPTION PRODUCT HIGHLIGHTS The AD625 is a precision instrumentation amplifier specifically 1. The AD625 affords up to 16-bit precision for user selected designed to fulfill two major areas of application: 1) Circuits re- fixed gains from 1 to 10,000. Any gain in this range can be quiring nonstandard gains (i.e., gains not easily achievable with programmed by 3 external resistors. devices such as the AD524 and AD624). 2) Circuits requiring a 2. A 12-bit software programmable gain amplifier can be config- low cost, precision software programmable gain amplifier. ured using the AD625, a CMOS multiplexer and a resistor For low noise, high CMRR, and low drift the AD625JN is the network. Unlike previous instrumentation amplifier designs, most cost effective instrumentation amplifier solution available. the ON resistance of a CMOS switch does not affect the gain An additional three resistors allow the user to set any gain from accuracy. 1 to 10,000. The error contribution of the AD625JN is less than 3. The gain accuracy and gain temperature coefficient of the 0.05% gain error and under 5 ppm/C gain TC performance amplifier circuit are primarily dependent on the user selected limitations are primarily determined by the external resistors. external resistors. Common-mode rejection is independent of the feedback resistor 4. The AD625 provides totally independent input and output matching. offset nulling terminals for high precision applications. This A software programmable gain amplifier (SPGA) can be config- minimizes the effects of offset voltage in gain-ranging ured with the addition of a CMOS multiplexer (or other switch applications. network), and a suitable resistor network. Because the ON 5. The proprietary design of the AD625 provides input voltage resistance of the switches is removed from the signal path, an noise of 4 nV/Hz at 1 kHz. AD625 based SPGA will deliver 12-bit precision, and can be programmed for any set of gains between 1 and 10,000, with 6. External resistor matching is not required to maintain high completely user selected gain steps. common-mode rejection. For the highest precision the AD625C offers an input offset voltage drift of less than 0.25 V/C, output offset drift below 15 V/C, and a maximum nonlinearity of 0.001% at G = 1. All grades exhibit excellent ac performance a 25 MHz gain band- width product, 5 V/ s slew rate and 15 s settling time. The AD625 is available in three accuracy grades (A, B, C) for industrial (40C to +85C) temperature range, two grades (J, K) for commercial (0C to +70C) temperature range, and one (S) grade rated over the extended (55C to +125C) tempera- ture range. REV. D Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. use, nor for any infringements of patents or other rights of third parties Tel: 781/329-4700 World Wide Web Site: (typical V = 15 V, R = 2 k and T = + 25 C, unless otherwise noted) AD625SPECIFICATIONS S L A AD625A/J/S AD625B/K AD625C Model Min Typ Max Min Typ Max Min Typ Max Unit GAIN 2 R 2 R 2 R F F F + 1 + 1 + 1 Gain Equation R R R G G G Gain Range 1 10,000 1 10,000 1 110,000 1 Gain Error .035 0.05 0.02 0.03 0.01 0.02 % Nonlinearity, Gain = 1-256 0.005 0.002 0.001 % Gain>256 0.01 0.008 0.005 % 1 Gain vs. Temp. Gain<1000 5 5 5 ppm/C GAIN SENSE INPUT Gain Sense Current 300 500 150 250 50 100 nA vs. Temperature 5 20 2 15 2 10 nA/C Gain Sense Offset Current 150 500 75 250 50 100 nA vs. Temperature 2 15 1 10 2 10 nA/C VOLTAGE OFFSET (May be Nulled) Input Offset Voltage 50 200 25 50 10 25 V vs. Temperature 1 2/2 0.25 0.50/1 0.1 0.25 V/C Output Offset Voltage 4 5 2 3 1 2 mV vs. Temperature 20 50/50 10 25/40 10 15 V/C Offset Referred to the Input vs. Supply G = 1 70 75 75 85 80 90 dB G = 10 85 95 90 100 95 105 dB G = 100 95 100 105 110 110 120 dB G = 1000 100 110 110 120 115 140 dB INPUT CURRENT Input Bias Current 30 50 20 25 10 15 nA vs. Temperature 50 50 50 pA/C Input Offset Current 2 35 1 15 1 5 nA vs. Temperature 20 20 20 pA/C INPUT Input Impedance Differential Resistance 1 1 1 G Differential Capacitance 4 4 4 pF Common-Mode Resistance 1 1 1 G Common-Mode Capacitance 4 4 4 pF Input Voltage Range 2 Differ. Input Linear (V ) 10 10 10 V DL G G G 12V V 12V V 12V V Common-Mode Linear (V) CM ( D) ( D) ( D) 2 2 2 Common-Mode Rejection Ratio dc to 60 Hz with 1 k Source Imbalance G = 1 70 75 75 85 80 90 dB G = 10 90 95 90 105 100 115 dB G = 100 100 105 105 115 110 125 dB G = 1000 110 115 110 125 120 140 dB OUTPUT RATING 10 V 10 V 10 V 5 mA 5 mA 5 mA DYNAMIC RESPONSE Small Signal 3 dB G = 1 (R = 20 k ) 650 650 650 kHz F G = 10 400 400 400 kHz G = 100 150 150 150 kHz G = 1000 25 25 25 kHz Slew Rate 5.0 5.0 5.0 V/ s Settling Time to 0.01%, 20 V Step G = 1 to 200 15 15 15 s G = 500 35 35 35 s G = 1000 75 75 75 s 2 REV. D