Research note Automatic lines impedance matching for reduction of coupled noise to an amplifier
DAVOOD KHALILI · International Journal of Electronics · 1988
Traditionally, a potentiometer and a capacitor have been used to balance (match) the impedances of lines at the inputs of amplifiers. This technique involves monitoring the output of the amplifier with oscilloscope and adjusting the potentiometer until the output (amplified noise) is minimized under the condition when a sensing device (transduser) is not yet activated. This method is time consuming and difficult especially when many channels (transducer + amplifier) are involved. An automatic impedance matching circuit was designed. By pressing a push button switch, the circuit automatically balances the input lines of an amplifier where it gets connected to, and when an LED is lit this indicates that impedance matching has taken place.