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Ground Up to Ground Down Receiver

IP.com Disclosure Number: IPCOM000082952D
Original Publication Date: 1975-Mar-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Gruodis, AJ: AUTHOR [+2]

Abstract

The circuit shown is an interface receive circuit which is capable of translating ground-up levels with a 0-->+5V swing at its input, into internal ground-down levels requiring a 0-->-1.5V swing at its output.

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Ground Up to Ground Down Receiver

The circuit shown is an interface receive circuit which is capable of translating ground-up levels with a 0-->+5V swing at its input, into internal ground-down levels requiring a 0-->-1.5V swing at its output.

The circuit is noninverting and uses a Schottky diode at its input instead of a TTL type transistor input, since the Schottky diode exhibits very low leakage and high reverse breakdown characteristics. In this way, the low emitter-base reverse breakdown voltage and subsequent Beta degradation of the input transistor is averted.

When the input is at its down level, Schottky diode D(1) conducts with current being supplied from the +V(Sup) supply through resistor R(1). Schottky diode D(2) and base-emitter diode T(2), formed by commoning the base to the collector, are both in a low-conduction state with the current through the devices being set by base resistor R(2).

(Image Omitted)

T(4) and T(5) are base-emitter diodes formed by commoning the base and collector of transistors T(4) and T(5). With T(6) ON, the circuit is capable of a high TTL type fan-out. A high dot function capability is also obtained as well.

With the input at its UP or most positive level, diode D(1) is reverse biased and T(3) turns ON with current being supplied from the +V(sup) through R(1). Diode D(2)and base-emitter diode T(2) are in a higher conduction state and the base current into T(3) is equal to;

(Image Omitted)

Proper diode and transistor biasing...