Micropower Buffered Variable Voltage Source
Category: Basic Circuits
Designer: RANA MUHAMMAD ADNAN KHALIL
Notes
This circuit is a micropower buffered variable rail-to-rail voltage source. Vout can be from within a few mV to a few 10ths of mV from supply rails. The actual o/p voltage achievable depends on the output impedance of the op-amp selected and the value of the load resistance. I/p to the +ve i/p terminal is set by the potentiometer, which can be of almost any value due to the high i/p impedance of the amp (Rin >~ 1000Gohm). In this circuit, 2Mohm potentiometer or higher is selected to limit the power consumption. This potentiometer selection can also be determined by other factors such as noise, physical size, cost and availability. Note that in this voltage source circuit, the voltage souce o/p is ratiometric to the supply voltage, which may be desirable in some applications as Vout and Vin values track V+ values. Alternatively, +ve i/p can also be connected to a fixed instead to set a temperature stable, fixed Vout. Recommended ICs are ALD1702, ALD1704, ALD1706, ALD2701, ALD2702.