JPS5815322A - Comparison circuit - Google Patents

Abstract

PURPOSE:To simplify the constitution without the need for the provision of a diode for temperature compensation, by using a PNP and an NPN transistor (TR) complementarily for the purpose of temperature compensation. CONSTITUTION:A resistor R6 is provided as an emitter resistor of a TRQ4 and a resistor R7 is provided as an emitter resistor of a TRQ6. The collector of the TR Q4 and Q5 is connected to ground. As for the TRQ4, a PNP TR being complementary to a TRQ1 is used. The way of temperature change characteristic is opposite to each other for the Q1 and Q4 and the effect of temperature is canceled. The emitter output of the Q4 is applied to the base of the PNP TRQ5 via a diode D5, the temperature change is opposite to each other for the D5 and the Q5 and the effect of temperature is canceled. Thus, no temperature diode is required for the output of a buffer Bi, i.e., a positive input terminal of a comparator COM.

Description

[Detailed description of the invention] The present invention relates to a comparison circuit.

FIG. 1 shows an example of a binarization circuit (comparison circuit) of a photoelectric conversion unit in a 7-axis device, particularly a circuit for determining whether an image is white or black. Signal 81 is the input signal for white/black determination target t1, signal 8. is determined by the reference signal. ratio I2 device COM
is the input signal and the output of the transistor Q, which is the signal 8. Compare the two and find out the size relationship〉white and black
A valued signal is obtained. A signal 81 is input to the positive end of the comparator COM via the buffer B1 diodes D1 to D4. Furthermore, this signal S is inputted to the base terminal of the transistor Q1 via a pace resistor R8 to produce an average value signal. The construction of the transistor Q1 is provided with a resistor, a resistor, C1, and C2, forming a charging/discharging circuit. It is inputted to the base end of the resistance loss voltage dividing signal-like transistor Q2, and further drives the diode D5 via the starter end of the resistor transistor Q2 and the starter resistor.

What is noteworthy about this circuit configuration is the function of the four series-connected diodes D1 to D4. Since the effects of temperature changes mainly appear between the base and the construction ivy, in the figure, the temperature changes of -4') are connected in cascade in the process up to obtaining the signal S. That is, the pace emitter of Ql, the base of C2, the 7 node cathode of diode D5, and the pace emitter of φ. In order to remove the four temperature change components caused by the cascade connection, four diodes D1 to D4 are connected in series in the same direction as this temperature change direction and with the same amount of change. In the comparator COM, the change in fK degree is the positive end, ! It is offset by being input at the negative end.

In such a conventional configuration, the temperature compensation means is an important technical element, but the use of four diodes to realize it leads to an increase in the number of circuit points, which is not at all preferable.

An object of the present invention is to provide a comparison circuit that can reduce the number of circuits.

The gist of the present invention resides in the complementary use of a PNP (PNP) and NPN (Pn) Tunsister for the purpose of temperature compensation.

FIG. 2 is a diagram showing a further embodiment of the present invention. The features of this embodiment are as follows:
providing a transistor in place of the transistor;
providing a transistor 9 instead of the middle transistor;
Transistor Q4. Q5's layer format iJ PNP type binding etc. The structure of #cTo will be explained based on the circuit configuration.

Provide a resistor side as the emitter resistor of transistor Q4,
The other end of the wrinkle resistor R6 is connected to the positive power supply instead of the ground side. Resistor R is used as the resistance of transistor 9.
7 is provided, and the other end of the resistor is connected not to the ground side but to the positive power source. The collector side of transistor 4, Q5, is grounded.

According to such a configuration, the output of the resistor R3 becomes conductive. The potential at the base end of the transistor Q4 becomes lower than the voltage between the base and the transistor Q4.
4 is conductive, and when it becomes high, it becomes non-conductive. The emitter terminal of the transistor Q4 has a high potential when it is non-conducting, and a low potential (approximately ground potential) when it is conducting. Therefore, this potential is passed through the diode D5 to the input 8 through the diode D5.
．． At the same time, depending on whether the potential applied to the base of the transistor 9 is larger or smaller than the base voltage of the wrinkle transistor 9, the transistor 9 is controlled and becomes conductive or non-conductive. The output 85 of the transistor value is compared with the input signal 5 SR applied via the buffer B by the comparator COM, and a binary output corresponding to the magnitude relationship is obtained.

In this configuration, the temperature change components of the transistor Q1 and the transistor Φ have opposite polarities and the effects of temperature cancel each other out. Furthermore, diode D5 (Matahiro D6
) and the transistor, the temperature change components appear with opposite polarities, so that the effects of temperature cancel each other out. Therefore, the positive terminal of buffer 1B and comparator COM has temperature compensation.
The diodes were no longer needed at all. Furthermore, accurate binarization detection has become possible.

According to the present invention, temperature compensation can be achieved with a simple circuit configuration.

[Brief explanation of the drawing]

1st! El is a diagram of a conventional example, and FIG. '2 is a diagram of an example of the present invention. Ql, Q4195...transistor, COM...-ratio we. Figure 1 Scream Figure 2 Scream

Claims (1)

[Claims] a first transistor to which a first input signal is applied; a charging/discharging circuit provided on the emitter output side of the first transistor; the second to which the output of the discharge circuit is applied;
a transistor having the same layer type as the second transistor; A comparator circuit comprising: a third transistor to which a voltage is applied; and a comparator that compares the output of the transistor of the IM5 with the first input signal and generates an output according to the magnitude relationship thereof.