Analog Tuning Voltage With Circuit Analog Signal Multiplexing
Original Publication Date: 1978-Feb-01
Included in the Prior Art Database: 2005-Feb-20
As shown in Fig. 1, the analog tuning circuit comprises operational amplifier 10 and field-effect transistor (FET) switch 11, with the source connected to the output of the amplifier and the drain connected in a feedback loop through resistor R1 to the inverting input of the amplifier. The output signal V(0) is taken from terminal 12, thereby eliminating any error contributed by the temperature-dependent impedance drift of the FET switch 11. This is illustrated by the following mathematical expressions for the circuit of Fig. 1, assuming an ideal amplifier. (Image Omitted) Thus, the output voltage V(0) is independent of the resistance R(ON) of the FET switch 11.