Browse Prior Art Database

CMOS/BiCMOS Switchable Current Source

IP.com Disclosure Number: IPCOM000108696D
Original Publication Date: 1992-Jun-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Carswell, K: AUTHOR

Abstract

Disclosed is a CMOS/BiCMOS current mirror circuit that can be switched off. The circuit has no VBE (VGS) mismatch and, when switched off, consumes no power.

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CMOS/BiCMOS Switchable Current Source

       Disclosed is a CMOS/BiCMOS current mirror circuit that
can be switched off.  The circuit has no VBE (VGS) mismatch and, when
switched off, consumes no power.

      Most switchable current mirrors have a VBE or VGS mismatch
between the reference and mirror.  This circuit does not have a
mismatch.

      Similarly, most CMOS/BiCMOS switchable mirrors only switch off
the mirror current.  The reference current is not switched, and
therefore only a 50% power reduction is realized when the mirror is
off.  This circuit saves all of the power when it is switched off.

      Fig. 1 shows a BiCMOS embodiment, and Fig. 2 shows a CMOS
embodiment.  When Ein of Fig. 1 is high, current flows through N1 and
T1, setting the base voltages of T1 and T2. The base voltage of T2
sets the current in the load.  When Ein is low, no current flows
through T1 and resistor R shuts off T1 and T2.