Non-linear digital to analog conversion by intermediate conversion to time interval

An improved digital-to-analog converter in which a digital signal is converted into a periodical pulse signal and than filtered to yield a direct current, said converter including an input means which converts a digital signal to a periodical pulse signal, a filter circuit including a filter for converting a pulse signal to direct current which serves as an input to an oscillator, wherein the improvement comprises:

• an electrical network which receives as input a periodical pulse signal and outputs a signal to said filter having for said pulse signal a charge time constant differing from its discharge time constant such that a non-linear relation is obtained between the value of the input signal to said network and the amplitude of the output signal of said filter circuit;
• said network serving as the input circuit to said filter, comprising:
• an input means to receive said periodical pulse signals;
• a first resistive means connected to said input means;
• a diode connected in parallel with said first resistive means;
• second resistive means connected in series to the output of said first resistive means and said diode;
• capacitive means connected in series to the output of said second resistive means and the input to said filter;
• said diode serving to shunt at least partially said resistive means;
• the output of said capacitive means being the output of said network and serving as input to said filter;
• said filter having an input means connected in series with the output of said network, said filter serving to smooth the signal applied to its input.