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Improved Differential Driver

IP.com Disclosure Number: IPCOM000037216D
Original Publication Date: 1989-Nov-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Perry, PE: AUTHOR

Abstract

This differential driver circuit has minimum cross-over skew of the differential output, clamped output voltage swing regardless of load, and uses minimum layout area. The complementary metal oxide silicon (CMOS) circuit uses complementary signals derived from circuit input to drive a source follower output stage.

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Improved Differential Driver

This differential driver circuit has minimum cross-over skew of the differential output, clamped output voltage swing regardless of load, and uses minimum layout area. The complementary metal oxide silicon (CMOS) circuit uses complementary signals derived from circuit input to drive a source follower output stage.

Referring to Fig. 1, the circuit (shown in block diagram form) is comprised of two identical differential drivers 10 and 12. Driver 10 has true input 14 and driver 12 has complement input 16. Both circuits 10 and 12 have negative tri-state input -TS and negative driver inhibit -DI inputs. Output pads 18 and 20 have a 160 ohm resistor R connected between them.

Circuitry used in each of the drivers 10 and 12 is shown in the circuit diagram of Fig. 2. Inputs -TI and -DI come in to NAND circuit 22. Output from NAND 22 goes to both inverter 24 and NOR circuit 26. Input 14 or 16 goes to NOR circuit 26 and to NAND circuit 28. Output from inverter 24 also goes to NAND 28. Output from NAND 28 goes to inverter 30 which then drives the gate of N-type transistor 32. Similarly, output of NOR 26 goes through inverter 34 and then to the gate of P-type transistor 36. Output from the circuit is brought out to pad 18 or 20 as shown in Fig. 1.

The circuit of Fig. 2 uses N-device 32 connected to VDD as shown to clamp the up level to at least a threshold (Vt) below VDD and P-device 36 connected to ground as shown to clamp the down level to at le...