JPH0648976Y2 - Temperature compensated FET amplifier - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to an RF amplifier using a field effect transistor (FET), and particularly to a field-effect FET amplifier with a wide operating temperature range and low power consumption. The present invention relates to a temperature compensation type FET amplifier suitable for application.

[Conventional technology]

Conventionally, the output voltage of the power supply used as the drain voltage of this type of FET amplifier is set to the voltage that outputs the specified RF saturation output power at high temperature when the RF saturation output power of the FET amplification circuit is the lowest. . For this reason, the power supply voltage is such that a constant drain voltage is always supplied in the entire input voltage range and the entire temperature range.

[Problems to be solved by the invention]

In the above-mentioned conventional FET amplifier, since the drain voltage of the FET amplifier circuit is constant, the RF saturation output power unnecessarily increases at a low temperature where the output power of the FET rises and flows to the FET. As long as the drain current increases and the efficiency of the power supply is constant, the power consumption of the FET amplifier also increases.

That is, since the drain voltage is constant with temperature in the conventional FET amplifier, as shown by the solid line in FIG. 2, the RF saturation output power and the drain current increase at low temperatures where the output power capability of the FET increases, so As long as the efficiency of the switching regulator is constant, the power consumption of the FET amplifier increases.

An object of the present invention is to provide a temperature compensation type FET amplifier which has a constant RF saturation output and low power consumption even with temperature fluctuation.

[Means for solving problems]

The temperature-compensated FET amplifier of the present invention is the output voltage of the switching regulator itself for supplying to the FET amplifier circuit,
The difference between the temperature of the FET amplifier circuit and the detection voltage of the temperature-sensitive element is found, and the duty of the on-time of the switching element is determined based on the relationship between this difference and the preset output voltage and the detected voltage of the temperature-sensitive element. So that FE
R according to the temperature fluctuation characteristics of the RF saturation output power of the T amplifier circuit
F Performs control so that the saturated output power becomes constant.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention. In the figure,
The FET amplifier 1 is composed of a switching regulator 3 and a FET amplifier circuit 4. The voltage supplied from the primary power supply 2 is converted by the switching regulator 3 and given to the FET amplifier circuit 4, and an RF input signal 12 is supplied to the FET amplifier circuit. It is amplified by 4 and output as RF saturated output power 13.

The FET amplification circuit 4 includes a FET 15, an input circuit 16 and an output circuit 17 before and after the FET 15, and a temperature sensitive element (for example, a temperature sensitive resistor) 18 that detects the temperature of the FET amplification circuit 4. In addition,
The input and output circuits shown in the figure have been simplified to avoid complexity of the description.

The FET 15 operates by receiving a gate voltage and a drain voltage from the switching regulator 3 to obtain an amplification function. These voltages pass through the choke circuits in the input circuit 16 and the output circuit 17, respectively, and the gate and drain terminals of the FET 15 are obtained. Given to.

On the other hand, the switching regulator 3 includes a voltage converter 5 that outputs a gate voltage and a voltage converter 6 that outputs a drain voltage.

The voltage converter 5 is an ordinary converter that outputs a constant voltage and supplies it as a gate voltage.

The voltage converter 6 is a power source that changes the output voltage depending on the temperature, and interrupts the voltage supplied from the primary power source 2 by the on / off operation of the duty which is the switching element (transistor) 14, and changes this alternating voltage. Thai Aether
9, rectified and smoothed by inductance 10 and capacitance 11, converted to desired output voltage, and supplied as drain voltage. At this time, the duty of the ON time of the switching element 14 that determines the desired output voltage is detected by detecting both the output voltage and the temperature information from the temperature sensitive element 18 of the FET amplifier circuit 4.
It is amplified by the error amplifier 8 and determined by the voltage-pulse width modulation circuit 7.

Next, the operation of the FET amplifier having the above configuration will be described.

Since the RF saturation output power 13 of the FET amplification circuit 4 is determined by the magnitude of the drain voltage applied to the FET 15, the drain voltage is set to the specified RF saturation output power at a high temperature when the RF saturation output power of the FET amplification circuit 4 becomes the minimum. Set the output voltage to the output voltage.

With reference to the drain voltage at high temperature where the RF saturation output power is the lowest, the drain voltage supplied from the switching regulator 3 is varied according to the temperature as shown by the alternate long and short dash line in FIG. It is constantly controlled against fluctuations.

The temperature information of the FET amplifier circuit 4 necessary to keep the RF saturation output power constant is detected by the temperature sensitive element 18, and the difference between this detected voltage and the output voltage of the switching regulator 3 itself is calculated (of the absolute value). The difference, and therefore the temperature sensing element is summed when it has a negative characteristic), this difference is amplified by the error amplifier 8 and is determined by the duty of the ON / OFF operation of the switching element 14 by the voltage pulse width modulation circuit 7. Replaced by voltage. As a result, the drain voltage can be lowered at a low temperature to make the RF saturation output power constant and the power consumption of the amplifier can be reduced as shown by the chain line in FIG.

At this time, the output voltage of the switching regulator is RF
The voltage required to keep the saturated output power constant is set in advance as a function of temperature, that is, a function of the detection voltage of the temperature sensitive element. Then, the negative feedback control of the output voltage is performed based on the difference between the actual output voltage and the detection voltage of the temperature sensitive element, and the preset relationship (the relationship based on the above-mentioned function) to obtain the RF saturation output power. Control.

In this way, the output voltage is the detection voltage of the temperature sensitive element,
In other words, it becomes possible to control the output voltage as a function of temperature, which causes disturbance of the output voltage (input voltage change or load current change).
It is possible to obtain a stable output voltage by compressing, etc., and it is possible to control the RF saturated output power to be constant against temperature fluctuation.

On the other hand, the switching regulator type power supply is different from the series regulator type power supply, and since the output voltage of the power supply is determined by the duty of the on time of the switching element 14, the output voltage can be changed without deterioration of the power conversion efficiency. There is no other problem even if the output voltage is changed due to temperature fluctuation. If the temperature is constant, the output voltage is constant in the fluctuation range of the primary power supply 2 (input voltage range of the FET amplifier 1).

Thus, in the case of the FET amplifier 1 according to the present invention, by changing the drain voltage according to the temperature information, the second
The RF saturated output power becomes constant against temperature fluctuations as shown by the chain line in the figure, and the increase in the drain current of the FET amplifier circuit at low temperature is also reduced, and the power consumption of the FET amplifier is almost constant together with the decrease in the drain voltage. And the power consumption is low over the entire temperature range.

In the present embodiment, the amplifier circuit 4 has been described as an example of a single-stage amplifier, but it goes without saying that the same can be applied to a multi-stage amplifier circuit.

[Effect of device]

As described above, the present invention obtains the difference between the output voltage of the switching regulator and the detection voltage of the temperature sensitive element that detects the temperature of the FET amplifier circuit, and the difference, the preset output voltage and the temperature detection value. The duty of the switching element on-time is changed based on the relationship with the voltage, and the drain voltage of the FET amplification circuit is changed, so the temperature compensation type has a constant RF saturation output power and low power consumption with respect to temperature fluctuations.
A FET amplifier can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a diagram showing temperature characteristics of conventional FET amplifiers and the present invention. 1 ... FET amplifier, 2 ... primary power supply, 3 ... switching regulator, 4 ... FET amplification circuit, 5,6 ... voltage converter, 7 ... voltage-pulse width modulation circuit, 8 ... error amplifier, 9 ... diode, 10 ... inductance , 11 ... Capacitance, 12 ... RF
Input signal, 13 ... RF saturation output power, 14 ... Switching element (transistor), 15 ... FET, 16 ... Input circuit, 17 ... Output circuit, 18 ... Temperature sensitive element.

Claims (1)

[Scope of utility model registration request] 1. A FET comprising an FET amplifier circuit and a switching regulator for supplying a voltage to the FET amplifier circuit.
In the amplifier, the switching regulator obtains a difference between an output voltage of itself for supplying to the FET amplification circuit and a detection voltage of a temperature sensitive element that detects the temperature of the FET amplification circuit, and the difference and a preset value. The temperature-compensated FET amplifier is configured to temperature-compensate the output voltage by changing the duty of the on-time of the switching element based on the relationship between the output voltage and the detected voltage of the temperature-sensitive element. .