JP2859461B2 - Temperature compensation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[Object of the Invention]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature compensating circuit used in, for example, a stabilized power supply circuit of an integrated circuit.

[0003]

2. Description of the Related Art For example, a bandgap circuit is well known as a conventional stabilized power supply. FIG. 2 shows a general band gap circuit. The emitter of the transistor Q1 is grounded, the collector and base of the transistor Q1 are connected, and the collector of the transistor Q2 is connected to the transistor Q4,
Connected to each base of Q6. The emitter of the transistor Q2 is connected to the power supply Vcc, and the base of the transistor Q2 is connected to the bases of the transistors Q3 and Q5 and the transistor Q4.
Connected to the collector. The emitters of the transistors Q3 and Q5 are connected to the power supply Vcc.

Further, the emitter of the transistor Q4 is grounded via a resistor R1. The emitter of transistor Q6 is grounded. Further, the emitter area ratio of the transistor Q1 to the transistor Q2 is 1: N.

In the bandgap circuit having the above-described configuration, the output current Iout supplied to the collectors of the transistors Q5 and Q5 can be expressed by the following equations.

Iout = (VT / R1) · 1nN (where VT = (KT / q), T: absolute temperature, K: Boltzmann constant, q = electron charge) That is, the output current is V
A current with a temperature coefficient of T flows. By using this output current, the temperature characteristics of the circuit can be compensated.

The above circuit can obtain an output current having a temperature coefficient of VT. However, this circuit generally has a lower p (current amplification factor) and fT performance than an npn transistor.
Since an np transistor is used as part of the circuit, an accurate current output proportional to VT cannot be obtained.

When the collector current flowing through the transistor Q1 is Ic1 and the collector current flowing through the transistor Q2 is Ic2, the emitter potential Vx of the transistor Q2 is
Vx = Ic2R1 = VT1n (Ic1Is1 / Ic2Is2) (where Is1 and Is2 are transistors Q1 and Q2, respectively)
Vx = VT1n (Ic1Is1 / Ic2Is2) = VT1nN from the difference between the emitter potentials of the transistors Q1 and Q2.

Here, if Ic1 and Ic2 are the same current, this voltage Vx becomes equal, so that the output current becomes Iout = (VT / R1) 1nN.

Here, when β of the pnp transistor is low, the base currents of the transistors Q2 and Q3 increase, the collector currents of the transistors Q1 and Q2 become unequal, and the output current Iout is A temperature characteristic is also added so that it is not exactly proportional to VT.

Another disadvantage is that the circuit scale is large in order to simply obtain a current proportional to VT.

[0012]

In the above-described circuit for obtaining an output current proportional to VT and performing temperature compensation, the output current is
There is a disadvantage that the current proportional to T cannot be output accurately.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a temperature compensating circuit having a simple structure in which a current proportional to VT flows accurately.

[Configuration of the Invention]

[0015]

According to the present invention, a voltage source which is stable with respect to temperature is connected to the bases of first and second transistors having an emitter area ratio of 1: N. And a second resistor connected between the emitter of the first transistor and a reference potential point.

[0016]

According to the above configuration, a current proportional to VT required as a circuit for temperature compensation can be accurately obtained with a simple configuration.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

In FIG. 1, a stabilized power supply circuit 1 is connected to the bases of transistors Q1 and Q2,
, Q2 are connected to each other via a resistor R1. The emitter of transistor Q1 is grounded via resistor R2.

In the circuit having the above configuration, the output current Ic2 of the transistor Q2 is given by Ic2 = (VT1nN / R1), and a current proportional to VT can be obtained.

Therefore, by using the stabilized power supply circuit, a current for temperature compensation proportional to VT can be generated, and since no pnp transistor is used, β
And can output an accurate current.

[0021]

As described in detail above, according to the present invention,
Since the configuration is simple and the pnp transistor is not used, it is hardly affected by β, and a current source proportional to VT for accurate temperature compensation can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a temperature compensation circuit according to the present invention.

FIG. 2 is a conventional circuit diagram.

[Explanation of symbols]

 1 stabilized power supply circuit Q1, Q2 ... transistors R1, R2 ... resistors

Claims (1)

(57) [Claims] 1. A constant voltage source having a constant predetermined voltage, first and second transistors having different emitter area ratios each having a base connected to the low voltage source, and
And a first transistor connected between the emitters of the second transistor.
And a second resistor having an emitter of the first transistor connected between reference potential points, and generating a current for temperature compensation from a collector of the first transistor. Temperature compensation circuit.