JPH06343012A - Collector loss detecting circuit - Google Patents

Abstract

PURPOSE:To detect the accurate collector loss of a transistor. CONSTITUTION:The collector current of a transistor TR 8 whose collector loss is to be detected is detected by a 1st TR 1. The collector-emitter voltage of the TR 8 is converted into a current by a resistor 9 and detected. The collector current detected by the TR 1 is multiplied by the collector-emitter voltage detected by the resistor 9 by a multiplier consisting of the 2nd-5th TR 2-5 respectively. Meanwhile the collector-emitter voltage detected by the resistor 9 as a current is applied to the multiplier via a current mirror consisting of the 6th and 7th TR 6 and TR 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a collector loss detection circuit for detecting a collector loss of a transistor and protecting the transistor.

[0002]

2. Description of the Related Art In recent years, semiconductor integrated circuits have tended to have higher densities, and particularly in power amplifier circuits, how to efficiently operate power amplifier transistors has become a problem. That means that the protection circuit design becomes important and accurate collector loss detection is required.

A conventional collector loss detection circuit will be described below. FIG. 2 shows a conventional collector loss detection circuit, 52 is a transistor for detecting collector loss, 5
1 is a transistor whose base is commonly connected to the transistor 52, 53 is the transistor 52 together with 54
, A resistor for detecting the collector-emitter voltage of the transistor, 54 is a resistor for adding the collector current of the transistor 51 and the collector-emitter voltage of the transistor 52, 55
Is a load resistance of the transistor 52, 56 is a resistance for flowing a current obtained by multiplying the collector current of the transistor 52 by a constant resistance ratio to the transistor 51, 57 is an input terminal,
Reference numeral 58 is an output terminal, 59 is a power supply terminal, and 60 is a ground terminal.

The operation of the conventional collector loss detection circuit thus configured will be described below. In FIG. 2, the resistor 54 has a voltage value obtained by dividing the collector-emitter voltage of the transistor 52 whose collector loss is to be detected by the resistor 53, and a value obtained by multiplying the resistance value of the resistor 54 by the collector current of the transistor 51. A voltage is generated by adding and. Since the collector current of the transistor 51 has a value obtained by multiplying the collector current of the transistor 52 by the resistance ratio of the resistors 55 and 56, the voltage drop of the resistor 54 depends on the collector current of the transistor 52 and the collector-emitter voltage. And are added values, and this value is output to the output terminal.

[0005]

However, in the above-described conventional configuration, the collector current and collector-emitter voltage of the transistor to be detected are detected and they are simply added, so that the true power is detected. However, if a transistor protection circuit is configured using a conventional collector loss detection circuit, the power can be used enough, but the collector-emitter voltage or collector current limits the usage, and the transistor is used up to its limit. There was a problem that could not be done.

The present invention solves the above-mentioned conventional problems. When the collector loss of a transistor is detected to protect the transistor, the collector current and collector-emitter voltage of the transistor are detected and they are multiplied. It is an object of the present invention to provide a collector loss detection circuit which detects an accurate collector loss by multiplying the collector loss by using.

[0007]

In a collector loss detection circuit of the present invention, a transistor whose base is commonly connected to a transistor whose collector loss is to be detected, and a collector of the first transistor and both emitters thereof are common. Second and third transistors forming a connected differential amplifier circuit, a fourth transistor in which the base and base and collector of the second transistor are commonly connected, and an emitter in common with the emitter of the fourth transistor A fifth transistor having a base and a collector commonly connected to a base of the third transistor;
And a constant current source connected to the common emitter of the fifth transistor and the other end of which is grounded, a constant voltage source commonly connected to the base and collector of the fifth transistor, and an emitter of the transistor whose collector loss is to be detected. A sixth transistor commonly connected to the base and the collector via a collector-emitter voltage detection resistor, a base commonly connected to the base of the sixth transistor, and a collector fourth and the base of the second transistor. A seventh transistor commonly connected to the base and collector of the transistor, and a resistor having one end commonly connected to the collector and output terminal of the second transistor are provided.

[0008]

The collector loss detection circuit of the present invention makes the collector current of the transistor whose collector loss is to be detected the first
It is detected by the transistor. The collector-emitter voltage of the transistor whose collector loss is desired to be detected is converted into a current by a collector-emitter voltage detection resistor connected to the emitter of the transistor whose collector loss is desired to be detected, and then detected. The collector current detected by the first transistor and the collector-emitter voltage detected by the collector-emitter voltage detection resistor are used by the second transistor, the third transistor, the fourth transistor, and the fifth transistor. Multiply using the configured multiplier. In this case, the collector-emitter voltage detected as a current by the collector-emitter voltage detection resistor is applied to the multiplier via the current mirror composed of the sixth transistor and the seventh transistor.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of a collector loss detection circuit according to an embodiment of the present invention.
In FIG. 1, 8 is a transistor whose collector loss is to be detected, 1 is a transistor whose base is commonly connected to the transistor 8, and 2 and 3 constitute a differential amplifier circuit in which the collector of the transistor 1 and both emitters are commonly connected. Transistors 4 are transistors in which the base of the transistor 2 is commonly connected to the base and collector, and 5 are transistors whose emitter is commonly connected to the emitter of the transistor 4 and whose base and collector are commonly connected to the base of the transistor 3.

A constant current source 13 has one end connected to the common emitter of the transistors 4 and 5 and the other end grounded, 14 a constant voltage source commonly connected to the base and collector of the transistor 5, 6 a transistor 8 A transistor having a base commonly connected to the base of the transistor 6 and a collector commonly connected to the base of the transistor 2 and the base and collector of the transistor 4. 10 is a resistor whose one end is commonly connected to the collector of the transistor 2 and the output terminal 18.
1 is the load resistance of the transistor 8 and 12 is the transistor 8
Is a resistor for passing a current obtained by multiplying the collector current of (1) by a certain resistance ratio to the transistor 1, 15 is an input terminal, 18 is an output terminal, 16 is a power supply terminal, and 17 is a ground terminal.

The collector loss detection circuit according to the embodiment of the present invention constructed as above will be described below. In the case of protecting the transistor by detecting the collector loss of the transistor, it is necessary to detect the correct collector loss. The transistor 1 has a base commonly connected to a transistor 8 whose collector loss is to be detected, and a collector current obtained by multiplying the collector current of the transistor 8 by the resistance value ratio of the load resistor 11 and the resistor 12 flows through the transistor 1. The collector current of the transistor 1 becomes the common emitter current of the differential amplifier composed of the transistors 2 and 3.

On the other hand, a voltage obtained by subtracting the voltage value of V _BE of the transistor 6 from the collector-emitter voltage value of the transistor 8 is applied to the resistor 9, that is, the current flowing through the resistor 9 is between the collector-emitter of the transistor 8. It is approximately equal to the voltage divided by the resistance value of the resistor 9. The current flowing through the resistor 9 is equal to the emitter current of the transistor 6, and also equal to the emitter current of the transistor 4 due to the current mirror formed by the transistors 6 and 7.

Since the transistors 4 and 5 are connected to the constant current source with their emitters connected in common, the emitter current of the transistor 4 is I _VCE , the current value of the constant current source is I ₀ , q is electric charge, and T is T. If the absolute temperature and κ are Boltzmann constants, the voltage difference ΔV _BE between the bases of both the transistor 4 and the transistor 5 is given by the formula [Equation 1].

[0014]

[Equation 1]

Here, ln represents a natural logarithm. in this case,
It is assumed that the saturation currents of both transistors 4 and 5 are equal.
On the other hand, the collector current I _OUT of the transistor 2 with respect to the input voltage difference ΔV _BE of the differential amplifier composed of the transistor 2 and the transistor 3 is given by the formula [Equation 2] when the common emitter current is I _C.

[0016]

[Equation 2]

Substituting equation [equation 1] into equation [equation 2] yields equation [equation 3].

[0018]

[Equation 3]

This means that the emitter current of the transistor 4 is multiplied by the common emitter current of the differential amplifier composed of the transistors 2 and 3, and the collector current I _OUT of the transistor 2 flows through the resistor 10, An equivalent voltage value obtained by multiplying the collector-emitter voltage value of the transistor 8 and the collector current of the transistor 8 is obtained at the output terminal 18.

As described above, according to this embodiment, when the collector loss of the transistor is detected and the transistor is protected, the collector current and collector-emitter voltage of the transistor are detected and the multiplier is used. Then, a collector loss detection circuit for accurately detecting the collector loss can be provided.

[0021]

The collector loss detection circuit of the present invention can detect an accurate collector loss by detecting the collector current and collector-emitter voltage of a transistor and multiplying them by using a multiplier. it can.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a collector loss detection circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional collector loss detection circuit.

[Explanation of symbols]

 1 Transistor (1st) 2 Transistor (2nd) 3 Transistor (3rd) 4 Transistor (4th) 5 Transistor (5th) 6 Transistor (6th) 7 Transistor (7th) 8 Transistor 9 Resistor (collector-emitter) Voltage detection) 10, 11, 12 Resistance 13 Constant current source 14 Constant voltage source 15 Input terminal 18 Output terminal 16 Power supply terminal 17 Ground terminal

Claims (1)

[Claims] 1. A first transistor having a base commonly connected to a transistor whose collector loss is to be detected, and a second amplifier constituting a differential amplifier circuit having a collector of the first transistor and both emitters commonly connected. A third transistor, a fourth transistor having a base and a base and a collector commonly connected to the second transistor, an emitter having a common connection to an emitter of the fourth transistor, and a base and a collector having the third transistor A fifth transistor commonly connected to the base of the transistor, a constant current source having one end connected to the common emitters of the fourth and fifth transistors and the other end grounded, and a base of the fifth transistor and A constant voltage source commonly connected to the collector and the emitter of the transistor whose collector loss is to be detected A sixth transistor commonly connected to a base and a collector via a collector-emitter voltage detection resistor, a base commonly connected to the base of the sixth transistor, and a collector first and second to the base of the second transistor. A collector loss detection circuit including a seventh transistor commonly connected to the base and collector of the fourth transistor, and a resistor having one end commonly connected to the collector and output terminal of the second transistor.