Bipolar log converter

Claim 2

A bipolar log converter comprising a. a differential input amplifier having one input receiving a bidirectional current signal and another input connected to circuit common of a DC power supply means, and an output providing a voltage representative of said current signal; b. a pair of transistors comprising PNP and NPN types with their bases at circuit common and their collectors connected to said input of said differential input amplifier receiving the current signal; c. a voltage biasing network for providing a current flow from said DC power supply means through the collector-emitter junctions of said transistors thereby placing said transistors into a conducting condition for nonlinear potential-current conversion; d. a pair of diodes series connected between the emitters of said transistors and at the common junction of said diodes connected to the output of said differential input amplifier thereby forming a feedback loop wherein said current signal is passed through one of said collector-emitter junctions and a diode to the output of said differential input amplifier for creating a potential; and e. means for providing from said potential a continuous potential signal representing the current signal whereby said potential signal has a polarity representative of the flow direction of the current signal and a magnitude representative of the logarithm of the current signal, and said potential signal changing polarity upon a change in flow direction of the current signal.

Claim 3

The bipolar log converter of claim 1 wherein the voltage biasing nEtwork includes a pair of shunting resistances in parallel with said transistors whereby the current flows through the collector-emitter junctions and through said shunting resistances are in a ratio of at least 1 to 1,000 so that the current flow through the collector-emitter junction remains substantially constant.

Claim 4

The bipolar log converter of claim 2 wherein the ratio of current flows is at least 1 to 100,000.

Claim 5

The bipolar log converter of claim 2 wherein a resistance bridge is connected between said emitters of said transistors to produce a potential signal corresponding to said potential created at one of said collector-emitter junctions.

Claim 6

The bipolar log converter of claim 4 wherein a voltage follower differential amplifier receives said potential signal at one input and the other input is connected through a temperature compensating resistance to circuit common and in a feedback loop to the output thereof whereby the voltage output signal at said output is representative of the current signal and corrected for temperature errors in said resistance bridge.

Claim 7

The bipolar long converter of claim 1 wherein the voltage biasing network includes a four-arm resistance bridge, first and second resistances in parallel with said transistors, and third and fourth resistances in parallel with said first and second resistances, the current flows through said collector-emitter junctions and through said first and second resistances being in a ratio of at least 1 to 1,000 whereby the current flow through said collector-emitter junctions remains substantially constant, said third and fourth resistances forming a resistance bridge to produce at the junction of said third and fourth resistances a potential signal corresponding to said potential created at one of said collector-emitter junctions.

Claim 8

The bipolar log converter of claim 6 wherein a voltage follower differential amplifier receives said output voltage at one input and the other input connected through a tempeature compensating resistance to circuit common and in a feedback loop to the output thereof whereby the potential signal at said output is representative of the current signal and corrected for temperature errors in said resistance bridge before applying said potential signal to said means for providing an output thereof.

Claim 9

The bipolar log converter of claim 6 wherein a second pair of transistors comprising PNP and NPN types are connected emitter-emitter with like types mounted on a common chip with the first mentioned pair of transistors, and said second pair of transistors connected with their collectors to the junction of said first and second resistances and with their bases connected in reverse phase to the junctions of said first and third, and second and fourth resistances whereby a temperature change in one of the collector-emitter junctions produces an out-of-phase current through one of said first and second resistances of said bridge thereby compensating for a temperature induced-current variation in the nonlinear potential-current conversion at the collector-emitter junctions.

Claim 10

A bipolar log converter comprising: a. a differential input amplifier having one input receiving a bidirectional current signal and another input connected to circuit common of a DC power supply means, and an output providing a voltage representative of said current signal; b. a pair of transistors comprising PNP and NPN types with their bases at circuit common and their collectors connected to said input of said differential input amplifier receiving the current signal; c. a voltage biasing network connected between positive and negative terminals of said DC power supply means and said transistors having their emitters connected between said positive and negative terminals whereby a current flow between the collector-emitter junctions places said transistors into a conducting condition for nonlinear potential-current conversion; d. a pair of diodEs series connected between said emitters of said transistors and the common junction between said diodes being connected to the output of said differential input amplifier forming a feedback loop current, and said diodes selectively gating said current signal through one of said collector-emitter junctions into said feedback loop for conversion of said current signal into a potential whose polarity is determined by which transistor has conducted said current signal; e. a resistance bridge connected between said emitters of said transistors producing a potential signal corresponding in polarity to the potential produced by one of the collector-emitter junctions; and f. means for providing a scaler indicia of said potential signal from said resistance bridge which indicia is the logarithm of the magnitude of said current signal applied to said differential input amplifier.

Claim 11

A bipolar log converter comprising: a. a differential input amplifier having one input receiving a bidirectional current signal and another input connected to circuit common of a DC power supply means, and an output providing a voltage representative of said current signal; b. a pair of transistors comprising PNP and NPN types with their bases at circuit common and their collectors connected to said input of said differential input amplifier receiving the current signal; c. a voltage biasing network connected between positive and negative terminals of said DC power supply means and said transistors having their emitters connected between said positive and negative terminals whereby a current flow between the collector-emitter junctions places said transistors into a conducting condition for nonlinear potential-current conversion; d. a pair of diodEs series connected between said emitters of said transistors and the common junction between said diodes being connected to the output of said differential input amplifier forming a feedback loop current, and said diodes selectively gating said current signal through one of said collector-emitter junctions into said feedback loop for conversion of said current signal into a potential whose polarity is determined by which transistor has conducted said current signal; e. a resistance bridge connected between said emitters of said transistors producing a potential signal corresponding in polarity to the potential produced by one of the collector-emitter junctions; and f. means for providing a scaler indicia of said potential signal from said resistance bridge which indicia is the logarithm of the magnitude of said current signal applied to said differential input amplifier.

Claim 12

The bipolar log converter of claim 9 wherein the voltage biasing network includes a four-arm resistance bridge, first and second resistances in parallel with the emitters of said transistors, and third and fourth resistances in parallel with said first and second resistances, current control means associated with said first and second resistances providing a low impedance current path in parallel with the collector-emitter junctions of said transistors whereby the current flows through the collector-emitter junctions and through the low impedance current path of the first and second resistances is in a ratio of at least 1 to 1,000 so that the current flow through the collector-emitter junctions remains substantially constant, and said third and fourth resistances form the resistance bridge to produce at the junction of said third and fourth resistances an output voltage corresponding to said antilog potential signal created at one of said collector-emitter junctions.

Claim 13

The bipolar log converter in claim 10 wherein said current control means vary current flow responsively to temperature changes in said first and second resistances whereby the current flow in said collector-emitter junctions remains substantially constant.

Claim 14

The bipolar log converter of claim 10 wherein said current control means include a second pair of transistors comprising PNP and NPN types connected emitter-emitter with like types mounted on a common chip with the first mentioned pair of transistors, and said second pair of transistors connected with their collectors to the junction of said first and second resistances and with their bases connected in reverse phase to the junction of said first and third, and second and fourth resistances whereby the collector-emitter junctions of said second pair of transistors provide a low impedance current path and a temperature change in one of the collector-emitter junctions produces an out-of-phase current through one of said first and second resistances of said bridge thereby compensating for a temperature induced-current variation in the nonlinear potential current conversion at the collector-emitter junctions.

Claim 15

The bipolar log converter of claim 9 wherein the ratio of current flows is at least 1 to 100,000.

Claim 16

The bipolar log converter of claim 9 wherein a voltage follower differential amplifier receives at one input the potential signal from said resistance bridge and the other input is connected through a temperature compensating resistance to circuit common and in a feedback loop to the output thereof whereby the potential signal at said output is representative of the current signal and corrected for temperature errors in said resistance bridge before applying said potential signal to said means for providing a readout.

Claim 17

The bipolar log converter of claim 9 wherein a feedback capacitance shunts the output and said one input receiving said current signal of said differential input amplifier whereby said capacitance compensates for rapid current polarity reversals as conduction terminates in one of said diodes and begins in The other of said diodes.

Claim 18

The bipolar log converter of claim 15 wherein a voltage follower amplifier is connected a first input to said output of said differential input amplifier and a second input to circuit common and said voltage follower amplifier has a feedback loop between said first input and output thereof and a series capacitance providing a current connection to said one input receiving said current signal of said differential input amplifier, and said series capacitance being a small fraction of said feedback capacitance of said differential input amplifier whereby the output voltage of said differential input amplifier moves smoothly voltagewise at slow rates of transition in conduction of said diodes and said voltage follower amplifier at fast rates of transition in conduction of said diodes has current gain to act through said series capacitance to regulate the output voltage of said differential input which moves voltagewise at a comparable rate to a slow rate of transition in conduction of said diodes.