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Maxim > Design Support > Technical Documents > Application Notes > A/D and D/A Conversion/Sampling Circuits > APP 1988
Maxim > Design Support > Technical Documents > Application Notes > Amplifier and Comparator Circuits > APP 1988
Keywords: low powered op amps, quad op amps, rail-to-rail inputs, rail-to-rail outputs, rail-to-rail op
amps, opamp
APPLICATION NOTE 1988
Circuit Enables PC-Based Voltage Measurements
Apr 10, 2003
Abstract: In its simplest form, the PC voltmeter consists of a 4-channel, 10-bit A/D converter (IC2) with a
few passive components, connected to the PC printer port via a 25-pin male D-type connector.
In its simplest form, the PC voltmeter of Figure 1 consists of section "A" alone: a 4-channel, 10-bit A/D
converter (IC2) with a few passive components, connected to the PC printer port via a 25-pin male D-
type connector. Power is derived from pins 2 and 3, and the circuit draws about 1mA.
Figure 1. This circuit and the associated Q-BASIC listing enable a PC to monitor and measure the
voltages on four input channels.
IC2's wide power-supply range (2.7V to 5.25V) allows operation from a variety of PC printer ports. The
voltage at pins 2 and 3 is about 5V for a lot of desktop machines, but for portables it is more likely to be
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