Browse Prior Art Database

Full Swing or Partial Swing Complementary Metal-Oxide Semiconductor Driver

IP.com Disclosure Number: IPCOM000117786D
Original Publication Date: 1996-Jun-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 91K

Publishing Venue

IBM

Related People

Cao, T: AUTHOR [+5]

Abstract

Disclosed is a Complementary Metal-Oxide Semiconductor (CMOS) circuit that provides a full swing output voltage between 0 Volts and 2.5 Volts and a partial swing voltage that swings between 0.6 Volts and 1.6 Volts. This circuit could be useful as part of an off chip driver that interfaces to other circuits that require different input voltages. Since only one circuit is used, layout space on the chip can be conserved and an extra power supply for partial swing output is also unnecessary.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Full Swing or Partial Swing Complementary Metal-Oxide Semiconductor
Driver

      Disclosed is a Complementary Metal-Oxide Semiconductor (CMOS)
circuit that provides a full swing output voltage between 0 Volts and
2.5 Volts and a partial swing voltage that swings between 0.6 Volts
and 1.6 Volts.  This circuit could be useful as part of an off chip
driver that interfaces to other circuits that require different input
voltages.  Since only one circuit is used, layout space on the chip
can be conserved and an extra power supply for partial swing output
is also unnecessary.

      Figs. 1A and 1B are used to illustrate the basis of this
circuit.  Fig. 1A shows a CMOS inverter circuit using a P-channel
device T1 and an N-channel device T2.  The supply voltage, VDD is
connected to the source of the P-channel device T1, and ground is
connected to the source of the N-channel device T2.  This
configuration forms a classic CMOS full swing inverting driver
circuit.

      If the power supply to devices T1 and T2 is reversed, as
illustrated in Fig. 1B the P-channel and N-channel devices act as a
source follower and will deliver a partial swing output.  When the
gate of N-channel device T2 in Fig. 1B is high, the output A will
attain a voltage that is equal to VDD - Vt (where VDD is the supply
voltage and Vt is the threshold of the N-channel device).  If the
power supply is 2.2 Volts and the threshold of the devices is 600mV,
the voltage at the output will be 1.6 Volts.  Similarly, when the
input is low, the P-channel device, T1 will turn on and the N-channel
device T2 will be turned off.  Since the P-channel device acts a
source follower, the output voltage will be equal to a threshold
voltage of 600mV.  A partial voltage swing...