A voltage comparator (24) compares the voltage with a threshold voltage (Vth) corresponding to a limited current and detects an excess current status.

An output end of the voltage comparator is connected with the control module.

A resistor-capacitor oscillator circuit (10) is provided and includes a voltage comparator circuit (12).

An all CMOS voltage comparator circuit which incorporates a strobed latch.

An output end of the sampling maintaining circuit is connected with the voltage comparator.

This short-circuit detect circuit (36) includes a voltage comparator (20), a voltage comparator (22), a constant current source (24), a switch (SW3) and a short-circuit detect capacitor (Cx).

A voltage comparator (16) is connected across the specimen terminals to sense effective voltage across the specimen (10).

A clock, time counter, a voltage comparator and voltage reference are used in determining a course time measurement.

The operational amplifier U2 is connected to the voltage comparator U6 and the analog switch U7.

A signal reference is provided by amplifier (20) through voltage comparator (34).

Each of the voltage comparator devices is arranged for being fed with a same input signal and for generating an own internal voltage reference .

A capacitor (20) is connected to an input terminal (14) of the voltage comparator circuit (12).

A current mirror (36) is coupled between the first and second input of the voltage comparator.

A resistor divider network (30) is coupled to an input terminal (16) of the voltage comparator circuit (12) for generating a reference voltage.

A voltage comparator unit determines whether the variations detected in the differential amplifier is above a predetermined threshold value.