Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Reexamination Certificate
2001-07-27
2004-02-03
Wells, Kenneth B. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With specific source of supply or bias voltage
C327S540000, C323S315000
Reexamination Certificate
active
06686795
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
This invention relates generally to monolithic reference current generators and, more specifically, to a very compact self-biasing current generator that can be implemented in a bipolar semiconductor process or in a complementary metal oxide semiconductor (CMOS) process.
In the field of analog integrated circuit (IC) design, it is very common to provide a reference current that is proportional to a reference voltage, the reference current being provided though a current mirror.
FIG. 1
shows a typical prior art circuit for providing a reference current lout at the output of a current mirror. An operational amplifier forces the junction between resistor R
1
and the source terminal of device M
1
to a reference voltage Vref, thereby generating a current I that is equal to Vref/R
1
through components M
1
, M
2
, and R
1
. While this circuit appears simple, it requires the operational amplifier along with its bias circuit. A reference current generator such as this is often used to provide stable current sources to critical analog circuits inside a chip. If the current generator requires another bias circuit elsewhere in the chip for its own biasing, it increases the size, power requirements, and complexity of the entire current reference circuit. The biasing circuit for the operational amplifier of
FIG. 1
will most likely be very simple and inaccurate, causing undesirable errors in the offset, offset drift, and other parameters of the operational amplifier.
It would therefore be advantageous to provide a self-biasing reference current generator that is compact and capable of implementation in a bipolar semiconductor process or a CMOS process and that generates a reference current output as well as the bias currents required by the rest of the circuit.
REFERENCES:
patent: 5087891 (1992-02-01), Cytera
Fairchild Semiconductor Corporation
Hein William E.
Wells Kenneth B.
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