JPS63296506A - Temperature compensation circuit - Google Patents

Abstract

PURPOSE:To make the gain of an amplifier stable in all the temperature range by controlling the variable attenuator at a prescribed temperature range in response to the temperature fluctuation so as to correct the gain fluctuation and giving a constant voltage to the variable attenuator in other temperature range. CONSTITUTION:A constant voltage element 14 such as a Zener diode, a voltage generating circuit including a thermosensing element 11 and a switch circuit 9 are provided, an output voltage of a voltage generating circuit changing in response to the temperature change at a constant temperature range is fed to a variable attenuator 20 and a constant voltage is impressed on the variable attenuator 20 in place of the output voltage at temperatures other than said temperature range. That is, the control voltage fed to the variable attenuator 20 is fixed to a voltage depending on the constant voltage element 14 under a temperature and the voltage in response to the change in the thermosensing element 11 is obtained at temperatures over it, then the gain compensation at a high temperature is made stable and the overcompensation at a low temperature is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a temperature compensation circuit for stabilizing the gain of an amplifier over a wide temperature range.

BACKGROUND OF THE INVENTION Amplifiers used in conventional industrial equipment, especially equipment installed outdoors, are required to operate stably over a wide temperature range. In this case, it is also important to realize a simple configuration in order to reduce the cost of the equipment.

An example of the above-mentioned conventional amplifier temperature compensation circuit will be described below with reference to the drawings.

FIG. 4 shows the configuration of a temperature compensation circuit of a conventional amplifier. The temperature characteristics of only the two-stage amplifier 1.2 are normally the 6th
As shown in the figure, the gain increases at low temperatures and decreases at high temperatures. Also, the amount of variation is the variation ΔG at high temperature.
H is large compared to the fluctuation ΔGL at low temperatures.

In order to compensate for the temperature fluctuations of the amplifiers 1 and 2 mentioned above, P
A method has been considered in which a variable attenuator using an IN diode 7 is controlled by temperature. 3 in Figure 4 is a typical PI
It is an N diode attenuator.

Depending on the DC voltage applied to terminal 8 in the figure, the attenuation characteristic as shown in FIG. 6 is exhibited. This characteristic usually exhibits a feature in which the amount of attenuation and the voltage change linearly above a certain voltage vA, but the amount of attenuation becomes steep when the voltage is below ■A.

In order to compensate for temperature fluctuations in the amplifiers 1 and 2 mentioned above, it is necessary to control the attenuation amount of the PIN diode attenuator 3 using a voltage that changes depending on the temperature. Although there are various temperature sensing elements for obtaining voltage changes depending on the temperature, a circuit using a positive temperature coefficient thermistor will be described here. Positive temperature coefficient thermistors have the characteristic that their resistance value increases as the temperature rises.

6 in FIG. 4 is a resistor, and 6 is a positive characteristic thermistor. Since the resistance value of the positive characteristic thermistor 6 changes depending on the temperature,
The DC voltage at the connection point 4 between the resistor 6 and the positive temperature coefficient thermistor 6 exhibits characteristics as shown in FIG. The DC voltage at this connection point 4 is applied to the PIN diode attenuator 3 to control its attenuation amount so that the gains of the amplifiers 1 and 2 are constant.

Problems to be Solved by the Invention However, in a temperature compensation circuit using an element having the above-mentioned configuration, the amount of change in gain on the high temperature side and low temperature side of the amplifier is different, so the change in gain is completely different from the change in the amplifier over the entire temperature range. It is very difficult to obtain an attenuation characteristic with an inverse characteristic from a PIN diode attenuator and its control temperature-voltage conversion circuit.

In other words, with the circuit configuration shown in Figure 1, if you try to compensate for the gain only on the high temperature side, the compensation will be too strong on the low temperature side, resulting in the characteristics shown in Figure 8. have.

The present invention solves the above problem by providing a compensation circuit that stabilizes the gain of the amplifier over the entire temperature range by limiting overcompensation of the gain of the amplifier at low temperatures.

Means for Solving the Problems In order to solve the above problems, the temperature compensation circuit of the present invention has the following features:
A voltage generating circuit including a constant voltage element such as a Zener diode, a temperature sensing element, and a switch circuit are provided, and the output voltage of the voltage generating circuit, which changes according to temperature changes in a certain temperature range, is applied to the variable attenuator. The present invention is characterized in that at temperatures outside the temperature range, a constant voltage is applied to the variable attenuator instead of the output voltage.

Function The present invention uses a switch circuit to fix the control voltage applied to a variable attenuator such as a PIN diode attenuator to a voltage determined by a constant voltage element below a certain temperature, and at higher temperatures to adjust the control voltage to a voltage determined by a constant voltage element. This has the effect of stabilizing gain compensation on the high temperature side as in the conventional example, and at the same time suppressing overcompensation on the low temperature side.

Example Embodiments of the present invention will be described below with reference to diagram M1.

In FIG. 1, 9 is a differential switch circuit using a Zener diode 14. The voltage determined by the resistor 10 and the positive characteristic resistor 11 is controlled by the emitter 7 follower transistor 12 and resistor 16, and the voltage determined by the resistor 13 and Zener diode 14 is controlled by the emitter follower transistor 16 and resistor 1θ. Control terminal 17 of the PIN diode attenuator 2o as voltage
Participating in

When the temperature changes, the resistance value of the PTC thermistor 11 changes, and the base voltage of the transistor 12 changes, but since the Zener diode 14 is a device whose temperature fluctuations are almost ignored, the base voltage of the transistor 160 does not change.

The voltage of the Zener diode 14 is selected so as to obtain an appropriate attenuation control voltage at an appropriate temperature based on the temperature characteristics of the amplifiers 18 and 19.

Then, even if the base voltage of the transistor 12 changes due to temperature change due to the positive temperature coefficient thermistor 11, as long as the base voltage of the transistor 16 determined by the aforementioned Zener diode 14 is lower than the control voltage output to the control terminal 17, the control voltage output to the control terminal 17 will be 16, the voltage is determined by the Zener diode 14.

On the other hand, as the temperature changes, the base voltage of the transistor 12 becomes
If it becomes higher than the base voltage of the transistor 16, the control voltage of the terminal 17 becomes a voltage determined by the transistor 12 and the polarity thermistor 11, that is, a voltage that changes depending on the temperature. This situation is shown in the temperature-voltage characteristics shown in FIG.

In this way, in the high temperature range where the gain fluctuations of the amplifiers 18 and 19 are large, the compensation circuit consisting of the temperature sensing element 11 and the attenuator 20 is changed with temperature to compensate for the gain fluctuation, while the gain fluctuation is small and the attenuation is low. In the low temperature range where the characteristics of the amplifier 2o change sharply, the control voltage applied to the attenuator 2o is fixed by the Zener diode 14 to keep the amount of attenuation constant, and as shown in FIG. The gain can be suppressed to only a small increase. In this way,
Zener diode 14 and transistor 12.15 2
It is possible to realize a gain compensation circuit over a wide temperature range with a very simple structure of a stone.

Effects of the Invention As described above, according to the present invention, in a circuit that corrects gain fluctuations of an amplifier using a voltage-controlled variable attenuator,
In a certain temperature range, the variable attenuator is controlled according to temperature fluctuations to compensate for gain fluctuations, and in other temperature ranges, a constant voltage is applied to the variable attenuator to prevent excessive compensation. This makes it possible to stabilize the gain of the amplifier over a wide temperature range.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a temperature compensation circuit according to an embodiment of the present invention, FIG. 2 is a temperature-voltage conversion characteristic diagram of the switch circuit in FIG. 1, and FIG. 3 is a temperature compensation characteristic diagram according to FIG. Figure 4 is a circuit diagram of a conventional temperature compensation circuit, Figure 5 is a temperature-gain characteristic diagram of an amplifier, Figure 6 is a characteristic diagram of the PIN diode attenuator in Figure 4, and Figure 7 is a temperature-gain characteristic diagram of the amplifier. The voltage conversion characteristic diagram, FIG. 8, is the temperature characteristic diagram of FIG. 4. 9...Switch circuit, 10,13.16...
... Resistor, 11 ... Temperature sensing element (positive temperature thermistor), 12.15 ... Transistor constituting the differential amplifier circuit, 14 ... Zener diode, 18 .19...Amplifier, 20...Variable attenuator. Name of agent: Patent attorney Toshio Nakao and 1 other person7-
Soft → Faku Ku Ku I/) (Ko Ha Ho Ku Ku I O e″ faction

Claims (2)

[Claims] (1) A voltage-controlled variable attenuator for correcting amplifier gain fluctuations due to temperature changes, a variable voltage generating means that includes a temperature sensing element and outputs a voltage that changes according to temperature changes, and constant voltage generating means that always generates a constant voltage regardless of the temperature; and variable voltage generating means that applies the output voltage of the variable voltage generating means to the variable attenuator within a certain temperature range, and at temperatures outside the above temperature range. and a switching circuit for applying a constant voltage of the constant voltage generating means to the variable attenuator instead of the output voltage of the temperature compensation circuit. (2) A patent that applies the output voltage of the variable voltage generating means to the variable attenuator on the high temperature side higher than a given temperature, and applies the constant voltage output of the constant voltage generating means to the variable attenuator on the low temperature side lower than the above temperature. A temperature compensation circuit according to claim 1.