Patent ID: 6879204
Filing Date: 2005-04-12
Classification: H03G

Abstract:
1. An exponential conversion circuit, comprising: a first voltage conversion circuit configured to convert first and second reference input voltages to first and second differential output voltages on the basis of a gain control signal; a second voltage conversion circuit configured to convert the first reference input voltage and a first control input voltage to a third differential output voltage on the basis of the gain control signal; an exponential conversion element configured to produce an output current which varies exponentially according to the third differential output voltage; and an impedance bridge including a first, a second, a third and a fourth transconductance elements and an amplifier configured to produce the gain control signal to provide to the first and second voltage conversion circuit according to the first and the second differential output voltages, the first transconductance element receiving the first differential output voltage, the second transconductance element receiving the second differential output voltage, the third transconductance element receiving the output voltage of the amplifier and the fourth transconductance element receiving a second control input voltage, and the amplifier producing the output voltage according to the difference between the output current of the first transconductance element and the output current of the second transconductance element.