JPS606574B2 - power amplifier - Google Patents

Description

[Detailed description of the invention] The present invention relates to a power amplifier.

FIG. 1 is a structural diagram of a power amplification MOSFET.

In FIG. 1, 1 is a semiconductor substrate, 2 is a source region, 3 is a drain region, 4 is an insulating layer, 5 is a source electrode, 6 is a gate electrode, 7 is a drain electrode, 8 is a metal such as gold or Mo,
9 is solder, 10 is a lead wire, 11 is a case, 12
is a terminal. As is well known, in a power amplification MOSFET, a semiconductor substrate 1 and a source region 2 are electrically connected, and also electrically connected to a case. This is to dissipate the heat generated by the semiconductor through the case and to use the case as one of the electrode pins. The other gate electrode 6 and drain electrode 7 are connected to terminals electrically insulated from the case. Figure 2 shows MOSFE for power amplification.
This is a source follower push-pull amplifier circuit using T.
In FIG. 2, 13 is the amplifier, 14 is an N-channel MOSFET, 15 is a P-channel MOSFET, 1
6 is a power supply, and 17 is a load.

MOSFETs 14 and 15, 16 a power supply, 17 a load, and 18 an output terminal.

FIG. 3 shows a power amplifier in which the circuit shown in FIG. 2 is constructed using MOSFETs having the structure shown in FIG. In FIG. 3, the same reference numerals as in FIG. 2 indicate the same parts, 19 is a heat sink, 20 is an insulating plate, 21 is a socket, 22 is a shunt, and 23 is an amplifier board. In Figure 3, the power amplification MOSFE
In order to generate a large amount of heat, T14 and T15 are attached to a heat radiator 19 via an insulating plate 20 with a socket 21. The heat sink 9 is electrically connected to a chassis 22, and a board 23 of a front-layer amplifier is installed in the chassis.
The cases of MOSFET1 4 and 15 are connected to the output terminal. MOSFET14, 15 case and heatsink 1
9 forms a capacitor together with an insulating plate 20, and the case force is 0-3 type, and the value of this capacitor is approximately 20.
It becomes Misaki F. Therefore, the output signal shown in FIG. 2 flows through this capacitor to the heat sink 19 and also to the chassis 22. Therefore, the preamplifier board 23 also has this chassis 22.
The output signal flowing through the amplifier is induced, causing oscillation of the amplifier and deterioration of the distortion rate. This tendency is more pronounced as the frequency increases.
This is because the higher the frequency of the signal, the more the signal passes through the capacitor formed between the MOSFET case and the heatsink and passes through the heatsink and the chassis. An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to obtain a stable power amplifier.

In order to eliminate the above-mentioned drawbacks of the prior art, the present invention provides a method for insulating a heat sink to which the power amplifying MOSFET is attached from the chassis of the amplifier when the case of the power amplifying MOSFET is connected to the output terminal of the power amplifier. or electrically connected via a resistor.

FIG. 4 shows an embodiment of the present invention.

In Fig. 4, the same symbols as in Fig. 3 indicate the same parts, and 2
4 indicates an insulator. In FIG. 4, the heat sink 19 is attached to the chassis 22 by an insulator 24.
4, the heat sink 19 and the chassis 22 are electrically insulated, and the output signal does not flow to the chassis. Therefore, no output signal is induced to the original amplifier board 23, and the amplifier operates stably. FIG. 5 shows another embodiment of the present invention. In FIG. 5, the same reference numerals as in FIG. The radiator 19 is connected to the chassis 22 via the insulator 24. In FIG.
The heat sink 19 is further connected to the chassis via a resistor 25. Therefore, the MOSFE
The output signal flowing to the chassis through the capacitor formed between T and the heatsink is lost by this resistance and does not flow to the chassis. In this way, the amplifier does not suffer from oscillation or distortion. Also, in terms of direct current, the heatsink and chassis are kept at the same potential. According to the present invention, a stable power amplifier can be made.

[Brief explanation of drawings]

Figure 1 is a structural diagram of MOSFET. Figure 2 is MOSFET.
FIG. 3 is a side view showing the structure of a power amplifier using MOSFET, FIG. 4 is a side view showing an embodiment of the power amplifier of the present invention, and FIG. The figure is a side view showing another embodiment of the power amplifier of the present invention. '4,'5...Power amplification transistor, 24
...Insulator, 25...Resistance. Figure O Figure '2 Figure O3 Figure 74 - Figure 〆);

Claims (1)

[Claims] 1 comprising a drain electrode and a source electrode provided on a semiconductor substrate, and a gate electrode provided insulated between the drain electrode and the source electrode, the source electrode being electrically connected to a case housing the semiconductor substrate; a MOSFET for power amplification that is connected to the source electrode, uses the source electrode as an output electrode, and radiates heat from the semiconductor substrate through the case;
A heatsink to which the case of the MOSFET is attached via an insulating plate to form a capacitor between the case and the case via the insulating plate; and an amplifier enclosure to which the heatsink is attached via an insulator. , connected between the heat radiator and the transparent body, has an impedance for a signal leaking from the MOSFET to the heat radiator via the capacitor, and connects the heat radiator and the transparent body with direct current. and a resistor that maintains the same potential.