A new concept of a Gm tuning circuit for voltage- or current-controlled transconductance circuits

A new concept of a transconductance (Gm) tuning circuit using switched-capacitor (SC) circuits for voltage- or current-controlled transconductance circuits is proposed. This concept uses an integrator which is controlled by time (or frequency) as a current-to-voltage converter for tuning. The Gm can be determined by the integrated time of the current from the transconductance circuit, the integration capacitor and the reference voltage(s). Moreover, the Gm control voltage produced by the proposed circuit has no ripple. The proposed circuit can tune operational transconductance amplifiers, MOS resistive circuits and so on. Finally, an offset voltage cancellation technique for the integrator is shown. SPICE simulations are performed to verify the performance of the proposed circuits.