Abstract: The measurement of a very low intensity of an electric current is carried out by 5 integrating the electric current over integration cycles having a time period ti and measuring a peak value of a sawtooth voltage at an integrated circuit output each time at the end of the integration cycle, whereat noise voltage components of a frequency above a cut-off frequency, which has a value of the order of magnitude (0,1×2?×ti)?1, being parts of a voltage of a noise generated in an operational amplifier comprised in the integrated circuit are filtered out of the said sawtooth voltage and noise components, which have the origin in the high-frequency voltage components of Johnson noise, which appear in the low-frequency spectral part of the sawtooth voltage as aliasing, are subtracted from a filtered sawtooth voltage.

Abstract: A voltage comparator where the difference of currents from transistors is converted into voltage, which is amplified and conducted to a gate terminal of a switching transistor. A source of a limiting transistor is connected to the gate terminal. The voltage at the gate terminal when the switching transistor is quiescent is equal to a value between eight and nine tenths of the switching voltage at the gate of the transistor, at which voltage the transistor triggers a switching in the output stage. A response to an input voltage change at one direction of the sign reversal of the difference of the input voltages is fast. The voltage comparator is robust and reliable with regard to temperature variations.

Abstract: The measurement of a very low intensity of an electric current is carried out by integrating the electric current over integration cycles having a time period ti and measuring a peak value of a sawtooth voltage at an integrated circuit output each time at the end of the integration cycle, whereat noise voltage components of a frequency above a cut-off frequency, which has a value of the order of magnitude (0.1×2?×ti)?1, being parts of a voltage of a noise generated in an operational amplifier comprised in the integrated circuit are filtered out of the said sawtooth voltage and noise components, which have the origin in the high-frequency voltage components of Johnson noise, which appear in the low-frequency spectral part of the sawtooth voltage as aliasing, are subtracted from a filtered sawtooth voltage.

Abstract: Output currents from differentially connected transistors (t1, t2) in a voltage comparator are subtracted from each other and the current difference is converted into voltage, which is amplified and conducted to a gate terminal (gtst) of a switching transistor (t7) at the input of an output stage. A source of a limiting transistor (t8?), whose gate is connected to a terminal (vsn) of the low supply voltage through two series-connected and diode-connected transistors (t8?, t8??) is connected to the gate terminal (gtst). The voltage at the gate terminal (gtst) when the switching transistor (t7) is quiescent is equal to a value between eight and nine tenths of the switching voltage Vsw at the gate of said transistor, at which voltage said transistor triggers a switching in the output stage. Said transistors are of the same type with a similar geometry and they operate in similar current conditions.

Abstract: A transmission of a signal through an isolation interface with a capacitive barrier is performed so that in an input circuit of the interface by integrating with an appropriate time constant the slope rates of the edges of signal replicas U1o± of the transmitted input signal Ui are adjusted and that the said signal replicas are differentiated either in an appropriate differentiating unit, whereat the time constants of these differentiating units are shorter than the rising and falling-off times of the signal replicas and are advantageously in the order of magnitude of 1 nanosecond or below. Therefore, in a circuit on the output side of the capacitive barrier no amplifier in front of voltage comparators is needed, which makes it possible that the pulse width is maintained extremely precisely. The data transmission is immune from the fast variation in the order of magnitude of 10 kV/&mgr;s of the potential difference between the voltage supplying sources for the input and the output circuits.