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Analog to Digital Converter

IP.com Disclosure Number: IPCOM000095885D
Original Publication Date: 1964-Aug-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Mackay, JB: AUTHOR

Abstract

This analog to digital converter circuit utilizes surface control transistors as the active elements. Each surface control transistor (SCT) has four electrodes: base, collector, emitter and a fourth electrode, termed the gate. Until the gate becomes at least 6 volts positive with respect to the emitter, the device behaves as a normal transistor. When a gate level of 6 volts is exceeded, inhibition of the collector current begins, until at +8 volts there is no collector current through the transistor for a base current of.2 milliamp. At higher base current levels a larger gate voltage swing is needed for complete inhibition of collector current.

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Analog to Digital Converter

This analog to digital converter circuit utilizes surface control transistors as the active elements. Each surface control transistor (SCT) has four electrodes: base, collector, emitter and a fourth electrode, termed the gate. Until the gate becomes at least 6 volts positive with respect to the emitter, the device behaves as a normal transistor. When a gate level of 6 volts is exceeded, inhibition of the collector current begins, until at +8 volts there is no collector current through the transistor for a base current of.2 milliamp. At higher base current levels a larger gate voltage swing is needed for complete inhibition of collector current.

Three stages of an N-stage analog to digital converter are shown. When input 10 is at 0 volts, a current flows from the +12 volt power supply through resistor 14, diode 16, resistor 18 to the -6 volt power supply. This keeps the potential at the anode of diode 20 at a low enough level to prevent SCT 22 from becoming conductive. SCT's 24 and 26 are likewise biased to nonconduction through identical conductive paths. When input 10 rises to a high enough voltage, the anode of diode 20 climbs to a voltage sufficiently positive to turn on SCT 22. The conduction of SCT 22 results in a lowering of the potential at output terminal 28. The down potential at terminal 28 is reflected through conductor 30 to the cathode of diode 32 causing it to clamp point 34.

Assuming that input 10 goes even more positive, Zener diode 36 finally conducts causing a potential rise at the cathode of diode 38.

As input 10 continues to rise, SCT 24 does not become...