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Maxim > Design Support > Technical Documents > Application Notes > A/D and D/A Conversion/Sampling Circuits > APP 429
Maxim > Design Support > Technical Documents > Application Notes > Digital Potentiometers > APP 429
Keywords: programmable gain amplifier, PGA, MAX532, programmable gain, programmable resistor, ac
gain control
APPLICATION NOTE 429
Programmable-Gain Amplifier, Using the MAX532
DAC
Nov 01, 2000
Abstract: This application note discusses how to use the MAX532 to build a programmable gain amplifier
(PGA) that's suitable for AC gain control. No external components are necessary. Equations are provided
to easily calculate the output values.
The MAX532 is a dual, 12-bit, voltage-output DAC. Access to the output amplifier's input terminals
allows it to be easily configured as a programmable-gain amplifier (PGA) suitable for AC gain control.
The circuit configuration is that of an inverting amplifier, with R2 replaced by the effective resistance of
the DAC ladder (Figure 1) and R1 replaced by internal feedback resistor RFB (Figure 2). In this circuit,
an AC signal is applied to the feedback resistor input and the output signal is tied to the DAC reference
input. The maximum signal at VOUT is limited by the amplifier's headroom from the supply rails (±12V to
±15V), which must be a minimum of 2.5V from either rail.
Figure 1. Fixed-gain inverting amplifier.
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