Analog to gray code converter

Claim 2

An analog to digital converter for converting an analog signal to a digital signal represented in Gray code, said converter comprising: input means for receiving an analog signal; a plurality of stages sequentially connected to operate serially on said analog signal to which said analog signal is applied from the input means, the stages including a chain of folding circuits each having input and output terminals, each of said circuits having a foldover voltage point which is matched to the midpoint of the output range of the previous folding circuit; and a separate threshold circuit associated with each of said folding circuits, each of said threshold circuits connected to the input of the associated folding circuit, such that the signal is applied to the next threshold circuit if above the foldover point and inverted and passed to said next threshold circuit if below said foldover point so as to produce a Gray code output bit while the corresponding foLding circuit passes on to the next stage an analog voltage representative of the location of the input with respect to the voltage range.

Claim 3

A converter as set forth in claim 1 wherein: said folding circuits each include a unity gain phase splitter having a negative slope transfer characteristic, said phase splitter being connected to a pair of parallel-connected diodes, the diodes selecting the more positive output of the splitter.

Claim 4

A converter as set forth in claim 2 wherein: said phase splitter includes a transistor having base, collector and emitter electrodes, said collector and emitter electrodes providing approximately the same resistance values, and said pair of diodes consists of a zener diode connected between said collector electrode and an output terminal of said folding circuit and the other diode connected between said emitter electrode and the output terminal, the zener diode, voltage being selected so as to match the foldover point to the midpoint of the output range of the previous folding circuit.

Claim 5

A converter as set forth in claim 2 wherein: said phase splitter includes a transistor having base, collector and emitter electrodes, a potentiometer coupled to said collector electrode and wherein said pair of diodes consists of a zener diode connected between said connector electrode and an output terminal of said folding circuit and the other diode connected between said emitter electrode and the output terminal, said potentiometer adjustable to vary the collector electrode supply voltage so as to match the folding point of each folding circuit to the midpoint of the output range of the previous folding circuit.

Claim 6

A converter as set forth in claim 1 wherein: each of said folding circuits includes an operational amplifier having an inverting input and a noninverting input, a diode being connected from said noninverting input to ground, whereby a positive input voltage cuts off said diode feeding the voltage directly to the noninverting amplifier input causing the amplifier to provide a gain of two output voltage whereas when a negative input voltage is applied, the diode grounds the noninverting amplifier input, causing the amplifier to act as a gain of two inverter.

Claim 7

A converter as set forth in claim 1 wherein: each threshold circuit includes a limiting amplifier, said amplifier serving to feed the analog signal directly to the next threshold circuit and a Gray code output bit is produced if the analog signal is above the midpoint of its input range while if the analog signal is below the midpoint range of the analog signal input, the analog signal is inverted and passed on to the next threshold circuit.

Claim 8

A converter as set forth in claim 6 wherein: said limiting amplifier of each of said threshold circuits includes a transistor having base, collector and emitter electrodes, a potentiometer being coupled to said base electrode, said transistor being adjusted to turn on and off precisely at the foldover voltage point by varying the potentiometer so as to set the necessary level of base electrode bias current.

Claim 9

An analog to digital converter for converting an analog signal to a digital signal represented in Gray code, said converter comprising: input means for receiving an analog signal; a plurality of stages sequentially connected to operate serially on said analog signal to which the analog signal is applied from the input means, the stages including a chain of of folding circuits each having input and output terminals, each of said circuits having a foldover voltage point which is matched to the midpoint of the output range of the previous folding circuit; said folding circuits each including a unity gain phase splitter having a negative slope transfer characteristic, said phase splitter being connected to a pair of parallel connected diodes, the diodes selecting the more positive output of the splitter; a separate threshold circuit associated with each of said folding circuits, Each of said threshold circuits connected to the input of the associated folding circuit such that the signal is applied to the next threshold circuit if above the foldover point and inverted and passed to said next threshold circuit if below said foldover point so as to produce a Gray code output bit while the corresponding folding circuit passes on to the next stage an analog voltage representative of the location of the input with respect to the voltage range; and each threshold circuit including a limiting amplifier, said amplifier serving to feed the analog signal directly to the next threshold circuit to produce the Gray code output.

Claim 10

An analog to digital converter for converting an analog signal to a digital signal represented in Gray code, said converter comprising: input means for receiving an analog signal; a plurality of stages sequentially connected to operate serially on said analog signal to which the analog signal is applied from the input means, the stages including a chain of of folding circuits each having input and output terminals, each of said circuits having a foldover voltage point which is matched to the midpoint of the output range of the previous folding circuit; said folding circuits each including a unity gain phase splitter having a negative slope transfer characteristic, said phase splitter being connected to a pair of parallel connected diodes, the diodes selecting the more positive output of the splitter; a separate threshold circuit associated with each of said folding circuits, Each of said threshold circuits connected to the input of the associated folding circuit such that the signal is applied to the next threshold circuit if above the foldover point and inverted and passed to said next threshold circuit if below said foldover point so as to produce a Gray code output bit while the corresponding folding circuit passes on to the next stage an analog voltage representative of the location of the input with respect to the voltage range; and each threshold circuit including a limiting amplifier, said amplifier serving to feed the analog signal directly to the next threshold circuit to produce the Gray code output.

Claim 11

An analog to digital converter for converting an analog signal to a digital signal represented in Gray code, said converter comprising: input means for receiving an analog signal; a plurality of stages sequentially connected to operate serially on said analog signal to which the analog signal is applied from the input means, the stages including a chain of folding circuits each having input and output terminals, each of the said circuits having a foldover voltage point which is matched to the midpoint of the output range of the previous folding circuit; said folding circuits each including a unity gain phase splitter having a negative slope transfer characteristic, said phase splitter being connected to a pair of parallel connected diodes, the diodes selecting the more positive output of the splitter; said phase splitter including a transistor having base, collector and emitter electrodes, said collector and emitter electrodes providing approximately the same resistance values, and said pair of diodes consisting of a zener diode connected between said collector electrode and an output terminal of said folding circuit and the other diode connected between said emitter electrode and the output terminal, the zener diode voltage being selected so as to match the foldover point to the midpoint of the output range of the previous folding circuit; a separate threshold circuit associated with each of said folding circuits, each of said threshold circuits sequentially connected to the input of the associated folding circuit such that the signal is applied to the next threshold circuit if above the foldover point and inverted and passed to said next threshold circuit if below said foldover point so as to produce a Gray code output bit while the corresponding folding circuit passes on to the next stage an analog voltage representative of the location of the input with respect to the voltage range; each threshold circuit including a limiting amplifier, said amplifier serving to feed the analog signal directly to the next threshold circuit; and said limiting amplifier of each of said threshold circuits including a transistor having base collector and emitter electrodes, a potentiometer being coupled to said base electrode, said transistor being adjusted to turn on and off precisely at the foldover voltage point by varying the potentiometer so as to set the necessary level of base electrode bias current.

Claim 12

An analog to digital converter for converting an analog signal to a digital signal represented in Gray code, said converter comprising: input means for receiving an analog signal; a plurality of stages sequentially connected to operate serially on said analog signal to which the analog signal is applied from the input means, the stages including a chain of folding circuits each having input and output terminals, each of the said circuits having a foldover voltage point which is matched to the midpoint of the output range of the previous folding circuit; said folding circuits each including a unity gain phase splitter having a negative slope transfer characteristic, said phase splitter being connected to a pair of parallel connected diodes, the diodes selecting the more positive output of the splitter; said phase splitter including a transistor having base, collector and emitter electrodes, said collector and emitter electrodes providing approximately the same resistance values, and said pair of diodes consisting of a zener diode connected between said collector electrode and an output terminal of said folding circuit and the other diode connected between said emitter electrode and the output terminal, the zener diode voltage being selected so as to match the foldover point to the midpoint of the output range of the previous folding circuit; a separate threshold circuit associated with each of said folding circuits, each of said threshold circuits sequentially connected to the input of the associated folding circuit such that the signal is applied to the next threshold circuit if above the foldover point and inverted and passed to said next threshold circuit if below said foldover point so as to produce a Gray code output bit while the corresponding folding circuit passes on to the next stage an analog voltage representative of the location of the input with respect to the voltage range; each threshold circuit including a limiting amplifier, said amplifier serving to feed the analog signal directly to the next threshold circuit; and said limiting amplifier of each of said threshold circuits including a transistor having base collector and emitter electrodes, a potentiometer being coupled to said base electrode, said transistor being adjusted to turn on and off precisely at the foldover voltage point by varying the potentiometer so as to set the necessary level of base electrode bias current.

Claim 13

An analog to digital converter for converting an analog signal to a digital signal represented in Gray code, said converter comprising: input means for receiving an analog signal; a plurality of stages sequentially connected to operate serially on said analog signal to which the analog signal is applied from the input means, the stages including a chain of folding circuits each having input and output terminals, each of said circuits having a foldover voltage point which is matched to the midpoint of the output range of the previous folding circuit; said folding circuits each including a unity gain phase splitter having a negative slope transfer characteristic, said phase splitter being connected to a diode, the diode electing the more positive output of the splitter; said phase splitter including a transistor having base, collector and emitter electrodes, a potentiometer coupled to said collector electrode, said potentiometer adjustable to vary the collector electrode supply voltage so as to match the folding point of each folding circuit to the midpoint of the output range of the previous folding circuit; a separate threshold circuit associated with each of said folding circuits, each of said threshold circuits connected to the input of the associated folding circuit such that the signal is applied to the next threshold circuit if above the foldover point and inverted and passed to said next threshold circuit if below said foldover point, each of said threshold circuits serving to determine whether its input is above or below the foldover point of the corresponding folding circuit so as to produce a Gray code output bit while the corresponding folding circuit passes on to the next stage an analog voltage representative of the location of the input with respect to the voltage range; and each threshold circuit including a pair of parallel emitter followers connected to the output of the preceding folding circuit, said emitter followers performing the folding operation by following only the most positive of their inputs, one of the two emitter followers being cut off most of the time.

Claim 14

An analog to digital converter for converting an analog signal to a digital signal represented in Gray code, said converter comprising: input means for receiving an analog signal; a plurality of stages sequentially connected to operate serially on said analog signal to which the analog signal is applied from the input means, the stages including a chain of folding circuits each having input and output terminals, each of said circuits having a foldover voltage point which is matched to the midpoint of the output range of the previous folding circuit; said folding circuits each including a unity gain phase splitter having a negative slope transfer characteristic, said phase splitter being connected to a diode, the diode electing the more positive output of the splitter; said phase splitter including a transistor having base, collector and emitter electrodes, a potentiometer coupled to said collector electrode, said potentiometer adjustable to vary the collector electrode supply voltage so as to match the folding point of each folding circuit to the midpoint of the output range of the previous folding circuit; a separate threshold circuit associated with each of said folding circuits, each of said threshold circuits connected to the input of the associated folding circuit such that the signal is applied to the next threshold circuit if above the foldover point and inverted and passed to said next threshold circuit if below said foldover point, each of said threshold circuits serving to determine whether its input is above or below the foldover point of the corresponding folding circuit so as to produce a Gray code output bit while the corresponding folding circuit passes on to the next stage an analog voltage representative of the location of the input with respect to the voltage range; and each threshold circuit including a pair of parallel emitter followers connected to the output of the preceding folding circuit, said emitter followers performing the folding operation by following only the most positive of their inputs, one of the two emitter followers being cut off most of the time.