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Start-Up Circuit for Bandgap Reference

IP.com Disclosure Number: IPCOM000101888D
Original Publication Date: 1990-Sep-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Gealow, JC: AUTHOR

Abstract

A self-biased bandgap reference circuit is shown which will disconnect from the reference circuit after start up, avoiding loading effects on the reference voltage output and interference with normal circuit operation.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 70% of the total text.

Start-Up Circuit for Bandgap Reference

       A self-biased bandgap reference circuit is shown which
will disconnect from the reference circuit after start up, avoiding
loading effects on the reference voltage output and interference with
normal circuit operation.

      Bandgap reference circuits are often used in high density DRAMs
for on-chip voltage regulators. A conventional self-biased reference
circuit is shown in Fig. 1. This circuit may power up in a stable
state with node A high, and node B low, Vref at ground, and no
current flowing through any of the devices (output zero). A start-up
circuit is shown which prevents the bandgap from remaining in this
state.

      Another conventional start-up circuit is shown in Fig. 2 with
bandgap reference. In this circuit, M5 always draws current from node
A which varies with the supply voltage creating an undesirable Vref
dependence on the supply voltage. To minimize this problem, the
channels of M1, M2, and M3 are extremely long.

      Referring to Fig. 3, by adding three new FETs (M6, M7 and M8)
to the bandgap reference circuit shown in Fig. 2, a new and improved
start-up circuit is created. In this design, the channel regions of
M1, M2, and M3 are made long and narrow to limit start-up current.
The channel of M4 is wide and has a moderate length. These four
transistors bias node D to a potential slightly greater than +1 volt
above ground.  If no current is flowing in the bandgap reference, M8
will be of...