Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Reexamination Certificate
1999-01-08
2001-01-16
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
C327S538000, C327S539000, C323S315000, C323S316000
Reexamination Certificate
active
06175265
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a current supply circuit and a bias voltage circuit.
2. Description of the Prior Art
FIG. 1
shows one example of a conventional current supply circuit
102
. As shown in
FIG. 1
, a first transistor
106
has an emitter
108
connected to a power supply terminal ground
124
through a first resistor
110
and a first collector
112
connected to a power supply terminal VCC
104
through a load. By applying a control voltage to a base of first transistor
106
, a collector current which is dependent on the control voltage is supplied to a load. The control voltage is created by a combination of a base-to-emitter voltage of a transistor
114
and a voltage caused by a current flowing through a second resistor
118
.
In addition, conventional current supply circuit
102
includes a bias voltage circuit. The bias voltage circuit includes a third resistor
122
that is connected to first collector
112
of first transistor
106
. The bias voltage circuit generates an output voltage utilizing a voltage drop by third resistor
122
at the connection point between third resistor
122
and first collector
112
.
There are various designs of current sources applicable to the circuit of
FIG. 1
, which have a positive temperature coefficient. In such cases, the output current varies corresponding to the temperature coefficient, as shown in FIG.
2
. That is, the output current supplied to the load greatly depends upon temperature, as shown in FIG.
2
. Furthermore, the output current has a temperature characteristic strongly reflecting an effect of a first term of the temperature coefficient, which increases the value of current supplied to the load as temperature rises.
Also, the bias voltage from such a current has a high temperature dependency which causes difficulty in control because the output current is determined by the collector current.
SUMMARY OF THE INVENTION
In the present invention a current supply circuit is configured such that a base-to-emitter voltage of a first transistor is amplified to generate a control voltage so that the control voltage is applied to a base of a second transistor. The control voltage is applied to the base of the second transistor to supply an output current to a load connected to a collector of the second transistor resulting in an output current that is not temperature dependent. That is, the base-to-emitter voltage of the first transistor with a negative temperature coefficient is amplified to provide a control voltage, which offsets an increase in positive temperature-coefficient output current, thus providing a flat temperature characteristic.
A current supply circuit is configured by comprising: a first transistor having a collector connected to a first potential and an emitter connected to a second potential; an amplifying circuit for amplifying a base-to-emitter voltage of the first transistor to generate a control voltage; and a second transistor having an emitter connected to the second potential through a first resistor, a base at which the control voltage is received, and a collector connected with a load supplied with an output current.
In an additional embodiment of the present invention, similar control can be performed in a bias voltage circuit. A bias voltage circuit is preferably configured by comprising: a first transistor having a collector connected to a first potential and an emitter connected to a second potential; an amplifying circuit for amplifying a base-to-emitter voltage of the first transistor to generate a control voltage; a second transistor having an emitter connected to the second potential through a first resistor and a base at which the control voltage is received, wherein a bias voltage is generated by a voltage drop caused due to a second resistor, connected to the collector of the second transistor.
REFERENCES:
patent: 4319180 (1982-03-01), Nagano
patent: 4736125 (1988-04-01), Yuen
patent: 5563502 (1996-10-01), Akioka et al.
patent: 40450830 (1991-10-01), None
patent: 50524154 (1993-01-01), None
patent: 4104517 (1992-04-01), None
Amster Rothstein & Ebenstein
Cox Cassandra
Nippon Precison Circuits Inc.
Wells Kenneth B.
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