JPS6331410Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE PRESENT DISCLOSURE The present invention relates to a power transistor having an improved stabilizing resistor for ensuring stable operation of the power transistor.

A power transistor is realized by connecting a plurality of small signal transistors in parallel depending on the power level. However, the parallel connection of transistors is not inherently stable, and has the property of aggravating thermal disturbances. Therefore, in order to operate the power transistor stably, a stabilizing resistor is inserted into the emitter.

FIG. 1 shows an equivalent circuit of a general power transistor, and FIG. 2 shows a structural plan view of a conventional power transistor in which a uniform stabilizing resistor is inserted. In the figure, 1 is the emitter terminal, 2 is the base terminal, and 3 is the emitter terminal.
4 is a collector terminal, 4 is a small signal transistor constituting a power transistor, and 5 is a stabilizing resistor.
All of the stabilizing resistors 5 have uniform resistance values and the same shape. If the value of the stabilizing resistor is R _e and the emitter current is I _e , feedback is applied due to the voltage drop R _e I _e . The larger the resistance value R _e is, the larger the amount of feedback becomes, and the power transistor operates more stably and uniformly.

However, increasing the value of the stabilizing resistor increases the loss, which lowers the cutoff frequency and lowers the power gain, especially in high-frequency transistors, so it is necessary to use the lowest possible value of the stabilizing resistor to ensure uniform operation. be.

In this invention, instead of a uniform stabilizing resistance, the square
It is characterized by arranging the stabilizing resistors in a cubic curve shape, and its purpose is to obtain a large stabilizing effect with small loss, which will be explained in detail below.

FIG. 3 is a distribution curve of non-uniform stabilizing resistance showing an embodiment of the present invention. The straight line 6 is a conventional uniform resistance, and the curve 7 is a 2.5 power curve-shaped non-uniform stabilizing resistance. FIG. 4 is a plan view showing the configuration of an embodiment of the present invention. In FIG. 4, the non-uniform stabilizing resistance is realized by varying the length of the resistor 5'. Since a low resistance value is a function of the width and length when the sheet resistance is kept constant, it can be achieved by varying either of them. Figure 5 shows the emitsuta width.
This figure shows the surface temperature distribution of a high-frequency power transistor with a saturation output of 0.5 W in the 900 MHz band, which has an emitter pitch of 2 μm, an emitter spacing of 8 μm, an average current of 5 mA per emitter, and 20 emitters.

Curve 8 has a uniform resistance of 15Ω, curve 9 has a central resistance of 15Ω
Curve 10 is the surface temperature distribution when the stabilizing resistor is arranged in a 2.5 power curve shape toward the end, and in a square shape. When arranged in a cubic curve, the temperature distribution will be as shown in curve 9.
It shows a distribution close to, or rather, good uniformity, but the current that flows transiently becomes large. This transient current becomes even more intense when raised to the third or fourth power. Therefore, the range of 2 to 3 is suitable for suppressing transient current and obtaining uniformity of temperature distribution. Compared to the case where a uniform resistor is inserted in this way, when a non-uniform resistor is inserted in the shape of a 2.5 power curve, the surface temperature distribution becomes flatter even though the overall resistance is smaller. In addition, the cut-off frequency is extended because the entire unit works uniformly and losses are reduced, and the power gain when operating in class C at 900 MHz increases from about 13.5 dB when a uniform resistor is inserted.
It was improved to about 13.8dB.

A two-dimensional thermal analysis is performed when a constant current is passed for a certain period of time, and the current distribution determined by the temperature conditions is calculated using Ebers-
Calculation using the successive approximation method, which involves calculating from Moll's equation, performing thermal analysis under those conditions, and determining the current distribution at that time, shows that uniform operation can be obtained with a small resistance value by including a nonuniform stabilizing resistor, and that the resistance By arranging the value distribution in the shape of a square to cube curve, it is derived that the stabilizing effect is large.

Figure 6 shows an example of the calculation results for the relationship between the emitter position and the emitter current, with curve 1
1 is uniform resistance, curve 12 is 0.5 power, curve 13 is 1
Curve 14 is the emitter current distribution when resistors are arranged in a square shape, and curve 15 is a cube shape.

As a result, it was found that it is effective to arrange the stabilizing resistors in the shape of a square-to-cubic curve, and it was found that this was in good agreement with the experimental results shown in FIG.

By inserting non-uniform stabilizing resistors in the present invention, it is possible to make the temperature distribution and current distribution more uniform than in the case of uniform resistors, and to improve the characteristics of the element. Furthermore, the present invention has the advantage that it can be used for high-frequency power transistors arranged in a straight line and low-frequency power transistors.

[Brief explanation of drawings]

Figure 1 is an equivalent circuit diagram of a general power transistor, Figure 2 is a configuration plan view of a conventional power transistor, Figure 3 is a distribution curve diagram of a non-uniform stabilizing resistor, and Figure 4 is an implementation of the present invention. FIG. 5 is a plan view of the structure of a power transistor showing an example, FIG. 5 is an actual measurement diagram of the surface temperature distribution of the power transistor, and FIG. 6 is a calculated curve diagram of the emitter current distribution. 1... Emitter terminal, 2... Base terminal, 4...
...Small signal transistor, 5'...uniform stabilizing resistor.

Claims (1)

[Scope of utility model registration request] In a power transistor having base electrodes arranged in a comb shape and an emitter electrode disposed between the base electrodes, one end of which is open and the other end of which is connected in common via a stabilizing resistor, the plurality of stabilizers 1. A power transistor characterized in that the value of the resistance is maximized at the center and gradually decreases toward the ends according to a square-to-cube curve.