A differential to single-ended converter includes a voltage-to-current converter that converts differential voltage input signals to differential current signals which differ by a difference current. A current mirror mirrors the first differential current signal. A substantially constant DC voltage level is established. A resistor conducts any difference in current between the mirrored current and the second differential current signal and translates this difference current to a single-ended voltage output signal. An input buffer provides the differential voltage input signals to the voltage-to-current converters.

A nonlinear transconductance provides a nonlinear output in response to a differential signal input. In a switch-type closed loop system, such as switching mode DC--DC converter of phase lock loop, the nonlinear transconductance amplifier provides a very fast response time. The nonlinear transconductance amplifier is a linear transconductance amplifier that has been modified to include a nonlinear output stage of current mirrors having resistive elements connected to the emitters of the diode connected transistors in the current mirrors. The nonlinearity of nonlinear transconductance amplifier is exponential such that when the differential signal at the inputs to the nonlinear transconductance amplifier is less than a predetermined value, the nonlinear transconductance amplifier provides an output or error correction signal that is nonlinear according to a second relationship, and that when the differential signal at the inputs to the nonlinear transconductance amplifier is greater than a predetermined value, the nonlinear transconductance amplifier provides an output or error correction signal that is nonlinear according to a second relationship.

A differential amplifier produces a collector current of an output side transistor as an output current signal. In this case, a power supply voltage or a closer voltage to the power supply voltage is supplied to a collector terminal of the output side transistor. First and second current mirror circuits produce a current signal in response to the output current signal. The produced current signal passes through a resistor, a terminal of which is connected to a reference voltage. When the produced current signal passes through the resistor, a voltage drop from the reference voltage occurs at the resistor. By utilizing the voltage drop at the resistor, an output voltage changing in response to two output voltage signals is produced.

A circuit constituting a system or a subsystem is composed of a cascade connection of a plurality of analog circuit cells. At least one of said analog circuit cells has either the current-sink input terminal and a current-source output terminal or a current-source input terminal and current-sink output terminal and operates in the current mode.

A variable electronic resistor (16), which can be varied by a control signal (Ust) at the control input (15), contains two parallel, signal paths (1 and 2) with identical components, of which one signal path carries a phase inverted input transmission signal and the other signal path carries a non phase inverted input transmission signal and which are additively joined at the output side. Each signal path contains a charge carrier channel (3) and a signal transmission stage (7) with a low impedance current input, located downstream of the output electrode (5) in the signal path of the charge carrier channel. The resistor of the charge carrier channel can be varied by a control voltage (Ust), which is common to both charge carrier channels, in a control electrode (14) of the semiconductor components (4).