Patent ID: 7659780
Filing Date: 2010-02-09
Classification: H03F,H03G

Abstract:
1. A gain control circuit, comprising: a resistor having a first terminal and a second terminal; an operational amplifier having an inverting terminal thereof electrically coupled to said first terminal of said resistor; a non-inverting terminal thereof; and an output terminal thereof; wherein the difference between an input voltage received by said second end of said resistor and a reference voltage received by said non-inverting terminal is amplified and delivered at said output terminal; and an amplifier circuit for transforming the voltage change of said operational amplifier output into a substantially exponential current change; wherein the output of said amplifier circuit is electrically coupled to said inverting terminal of said operational amplifier; a first current source and a second current source connected to the output of said amplifier circuit, wherein the sum of the amplifier circuit output current and said first current source is equal to said second current source; and a forward-biased bipolar diode circuit connected between said first current source and the output of said amplifier circuit.