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Cmos Hysteresis Receiver

IP.com Disclosure Number: IPCOM000061861D
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Wissel, L: AUTHOR

Abstract

A receiver circuit is described which achieves switching voltage hysteresis required for noise immunity in a simple and easily analyzed configuration. This circuit receives a non-complementary metal oxide semiconductor (non-CMOS) level, e.g., transis transistor logic (TTL) or a lower General Purpose Interface (GPI) input signal Vin and translates it to a CMOS level output signal Vout. The receiver employs a linear differential amplifier (LDA), a voltage divider, transistor TR1 and TR2, which establishes a reference voltage Vref, and a transistor Tr which alte the characteristics of the voltage divider to cause Vref to switch between desired high and low hysteresis switchpoint voltages.

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Cmos Hysteresis Receiver

A receiver circuit is described which achieves switching voltage hysteresis required for noise immunity in a simple and easily analyzed configuration. This circuit receives a non-complementary metal oxide semiconductor (non-CMOS) level, e.g., transis transistor logic (TTL) or a lower General Purpose Interface (GPI) input signal Vin and translates it to a CMOS level output signal Vout. The receiver employs a linear differential amplifier (LDA), a voltage divider, transistor TR1 and TR2, which establishes a reference voltage Vref, and a transistor Tr which alte the characteristics of the voltage divider to cause Vref to switch between desired high and low hysteresis switchpoint voltages.

Voltage levels in the following description of operation of the circuit shown in the figure are for the case of a TTL level signal driving Vin.

When Vin is low (less than 0.8 volts), Vout is low and transistor Tr does not conduct. Vref is set to 2.0 volts by the voltage divider comprised of diode connected transistors TR1 and TR2. As Vin rises above 2.0 volts, Vout switches high, turning transistor Tr on and pulling Vref to 0.8 volts. When Vin falls below
0.8 volts, Vout switches low, turning transistor Tr off and resetting Vref to 2.0 volts. Thus, hysteresis is established by switching transistor Tr in and out of the Vref voltage divider circuit. The hysteresis switch points are determined only by the static characteristics of transistors TR1, TR2 and Tr....