Logarithmic function generator utilizing an exponentially varying signal in an inverse manner

Claim 2

An electrical function generator comprising: first pulse generator means; voltages means connected to the output of said first pulse generator means and responsive to the pulses provided thereby for generating voltages which have the same period as said pulses, said generated voltage s varying exponentially with time; first comparator means, said first comparator means having a pair of input terminals, a first of said comparator input terminals being connected to receive said exponentially varying voltages; means for applying a signal commensurate with an input signal to said first comparator means second input terminal whereby said first comparator means will provide control signals indicative of equality between said exponentially varying voltages and said signal commensurate with the input signal; means for amplifying said signal commensurate with the input signal; second voltage comparator means, said second comparator means being connected to receive said exponentially varying voltages and the output of said amplifying means, said second comparator means providing control signals indicative of equality between said exponentially varying voltages and said amplified signal commensurate with the input signal; and means responsive to the control signals from said first and second comparator means for generating a signal commensurate with the logarithm of the input signal.

Claim 3

The apparatus of claim 1 wherein said means for generating a signal commensurate with the logarithm of the input signal comprises: second pulse generator means responsive to said equality signals provided by said first comparator means for generating pulses having A width commensurate with the period said exponentially varying signals exceed the magnitude of said signal commensurate with the input signal; third pulse generator means responsive to said equality signals provided by said second comparator means for generating pulses having a width commensurate with the period said exponentially varying signals exceed the magnitude of said amplified signal; summing means connected to receive and add the pulses generated by said second and third pulse generating means; and means responsive to the summed pulses appearing at the output of said summing means for averaging said pulses.

Claim 4

The apparatus of claim 2 wherein said first pulse generator means comprises: astable multivibrator means.

Claim 5

An electrical function generator comprising: first pulse generator means; means connected to the output of said first pulse generator means and responsive to the pulses provided thereby for generating voltages which have the same period as said pulses, said generated voltages varying exponentially with time; first comparator means, said first comparator means having a pair of input terminals, a first of said comparator input terminals being connected to receive said exponentially varying voltages; means for applying a signal commensurate with an input signal to said first comparator means second input terminal whereby said first comparator means will provide control signals indicative of equality between said exponentially varying voltages and said signal commensurate with the input signal, said first comparator means including differential amplifier means having said first pulse generator means output signals and said signal commensurate with the input signal applied as inputs thereto, and differentiator means connected to the output of said differential amplifier means and responsive to changes in polarity of said amplifier output signal for generating said control signals; and signal generating means responsive to said control signals indicative of equality for generating a signal commensurate with the logarithm of the input signal, said signal generating means comprising second pulse generator means responsive to said control signals indicative of equality for generating pulses having a width commensurate with the period said exponentially varying signals exceed the magnitude of said signal commensurate with the input signal, and means for averaging the pulses provided by said second pulse generator means.

Claim 6

An electrical function generator comprising: first pulse generator means; means connected to the output of said first pulse generator means and responsive to the pulses provided thereby for generating voltages which have the same period as said pulses, said generated voltages varying exponentially with time; first comparator means, said first comparator means having a pair of input terminals, a first of said comparator input terminals being connected to receive said exponentially varying voltages; means for applying a signal commensurate with an input signal to said first comparator means second input terminal whereby said first comparator means will provide control signals indicative of equality between said exponentially varying voltages and said signal commensurate with the input signal, said first comparator means including differential amplifier means having said first pulse generator means output signals and said signal commensurate with the input signal applied as inputs thereto, and differentiator means connected to the output of said differential amplifier means and responsive to changes in polarity of said amplifier output signal for generating said control signals; and signal generating means responsive to said control signals indicative of equality for generating a signal commensurate with the logarithm of the input signal, said signal generating means comprising second pulse generator means responsive to said control signals indicative of equality for generating pulses having a width commensurate with the period said exponentially varying signals exceed the magnitude of said signal commensurate with the input signal, and means for averaging the pulses provided by said second pulse generator means.

Claim 7

The apparatus of claim 2 wherein said first comparator means comprises: differential amplifier means having said first pulse generator means output signals and said signal commensurate with the input signal applied as inputs thereto; and differentiator means connected to the output of said differentiator amplifier means and responsive to changes in polarity of said amplifier output signal for generating said control signals.

Claim 8

The apparatus of claim 4 wherein said means for generating an exponentially varying voltage comprises: differentiator means connected to receive said first pulse generator means output pulses.

Claim 9

The apparatus of claim 2 wherein said means for generating an exponentially varying voltage comprises: differentiator means connected to receive said first pulse generator means output pulses.

Claim 10

The apparatus of claim 5 wherein said means for generating an exponentially varying voltage comprises: differentiator means connected to receive said first pulse generator means output pulses.

Claim 11

An electrical function generator comprising: first means for generating voltages whose amplitudes vary exponentially with time from preselected peak amplitudes; first comparing means for comparing said exponentially varying voltages with an input voltage signal and for providing control signals indicative of equality between said exponentially varying voltages and said input voltage signal; second comparing means for comparing exponentialLy varying voltages with peak amplitudes, which are at a predetermined relationship with respect to the peak amplitudes of the exponentially varying voltages compared in said first comparing means, with a voltage signal having an amplitude which is at a selectable relationship with respect to the input voltage signal, said second comparing means providing control signals indicative of equality between said exponentially varying voltages and the voltage signal compared therein; and output means responsive to the control signals from said first and second comparator means for generating a signal commensurate with the logarithm of said input voltage signal.

Claim 12

An electrical function generator comprising: first means for generating voltages whose amplitudes vary exponentially with time from preselected peak amplitudes; first comparing means for comparing said exponentially varying voltages with an input voltage signal and for providing control signals indicative of equality between said exponentially varying voltages and said input voltage signal; second comparing means for comparing exponentialLy varying voltages with peak amplitudes, which are at a predetermined relationship with respect to the peak amplitudes of the exponentially varying voltages compared in said first comparing means, with a voltage signal having an amplitude which is at a selectable relationship with respect to the input voltage signal, said second comparing means providing control signals indicative of equality between said exponentially varying voltages and the voltage signal compared therein; and output means responsive to the control signals from said first and second comparator means for generating a signal commensurate with the logarithm of said input voltage signal.

Claim 13

The apparatus as recited in claim 9 wherein the peak amplitudes of the exponentially varying voltages compared in said second comparing means and definable as P2 means are less than the peak amplitudes of the exponentially varying voltages compared in said first comparing means, definable as P1.

Claim 14

The apparatus as recited in claim 10 wherein P2/P1 (1)/10.