Patent ID: 7342328

Claim:
A circuit for controlling an output of a slave supply in a defined relationship to a time-varying master signal, the slave supply having a slave output terminal and a feedback input terminal, the circuit comprising: a charging circuit for supplying a drive signal to a ramp generator circuit configured to generate the master signal, the charging circuit having first and second current sources for selectably sourcing current to or sinking current from the ramp generator circuit; a tracking input terminal for receiving a tracking signal responsive to the master signal; a circuit output terminal; an operational amplifier that is coupled to the tracking input terminal and that accepts an input signal and a reference signal and outputs an op amp output signal; and a third current source coupled to the circuit output terminal that generates output current responsive to the op amp output signal, the output current having a magnitude that forces the output of the slave supply to behave in the defined relationship to the master signal when the circuit output terminal is coupled to the feedback input terminal, and the coupling of the third current source to the circuit output terminal presenting a high impedance to the feedback input terminal.