JPH01101002A - Semiconductor device - Google Patents

Abstract

PURPOSE:To improve a diode element characteristic by connecting two pairs of external leads to be faced to two pairs of electrodes on an insulator, connecting one pair of the electrodes among the two pairs by means of a diode and a fine metallic line, mounting and connecting a capacitor to one side of the pair of the electrodes, and connecting the counter electrode of the capacitor to the electrode pair of the other side. CONSTITUTION:When an input power is made sufficiently large and a current flows to a PIN diode 1, the resistance of the diode is lowered, and it is considered to be a short circuit. At such a time, when a capacitor 2 of a capacity C1 to generate a serial resonance with an L1 to a signal frequency is inserted in series to the L1. Since an impedance to see the diode from an input port is made into the short circuit, a total reflection is executed. When the input power is sufficiently small, the PIN diode 1 is made into a high resistance, and a signal is transmitted from a line 12 to a line 13. One part of the signal flows into the side of the diode element 1. In order to prevent it, a parallel resonance with the capacity in a diode vicinity is made to occur by the circuit of an inductance L3 and a capacitance C2. Thus, a high impedance can be realized, and losses can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device, and particularly to the structure of a diode limiter for over-input power protection used in a radar device.

[Conventional technology]

Generally, an over-input protection limiter circuit needs to propagate the input without loss at low input power levels, and prevent the input from propagating as much as possible at over-input power levels, thereby suppressing over-input to the low-noise amplifier. For this reason, a limiter circuit has conventionally been constructed using a diode having a PIN structure and utilizing the fact that the series resistance of the diode changes depending on the current flowing through the diode.

FIGS. 4(a) and 4(b) show a circuit diagram of an example of a conventional limiter circuit and its equivalent circuit diagram. That is, line 2
A diode l is connected to the center of the line 25, and a signal source 20 having a signal source resistance 21 and a load resistance 22 are connected to both ends of the line 25.

[Problem that the invention seeks to solve]

As mentioned above, in the over-input protection limiter circuit, a circuit such as a low-noise amplifier or mixer is connected after this circuit, so if there is a loss in the limiter circuit, this becomes an input circuit loss and the receiving sensitivity of the low-noise amplifier is affected. make things worse.

Now, if the signal frequency is 10 GHz, and the input signal is weak and no current flows through the diode, and it exhibits high resistance, and if the case capacitance is 0.2 PF, the power supplied to the load in the case shown in Figure 4 is produces a transmission loss of 0.4 dB.

On the other hand, at the time of excessive input, the diode 1 exhibits a low resistance, and in the case of FIG. 4, the input power is reflected and should not be propagated to the load. However, as this equivalent circuit, Fig. 4(b)
When considering, the internal inductance Ls is 0.2nH
Even if the resistance is only 12.6Ω at 10GHz. Therefore, the signal is not reflected back to the signal source side, but is passed to the load side. In this case, even if the resistance of the diode is OΩ, the input signal appears on the load side attenuated by about 7 dB. As described above, even if the resistance value of the Daitoto element is sufficiently high or low, there is a drawback that sufficient characteristics cannot be obtained due to the influence of the external circuit. That is, in the conventional configuration, there was a problem in that the low loss and high isolation of the diode itself was impaired in the microwave band due to parasitic elements such as wire inductance and case capacitance near the diode.

SUMMARY OF THE INVENTION An object of the present invention is to solve such problems and provide a semiconductor device in which impedance is canceled by the addition of parasitic elements using a series/parallel resonant circuit placed near the element, and element characteristics are improved.

[Means for solving problems]

The structure of the present invention includes a metal base, a diode element placed on the metal base using the metal base as one electrode, and two pairs of insulators placed on the metal base around the diode element. In a semiconductor device including electrodes respectively arranged on these insulators and thin metal wires connecting these electrodes and the diode, two pairs of external leads are connected opposite to the electrodes on the insulators. Of these two pairs, one pair of electrodes is connected to the diode with a thin metal wire, and a capacitor having a capacitance that resonates at the inductance of the thin metal wire and the frequency used is mounted on one of the pair of electrodes and connected to the diode. The capacitor is characterized in that a counter electrode thereof is connected to another pair of electrodes orthogonal to the pair of external leads.

〔Example〕

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

1(a) and 1(b) are a partially cutaway plan view and internal sectional view of an embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of FIG. 1. In this embodiment, on a metal base 5 provided with a heat sink 6 and mounting screws 7, insulators 4 having electrodes 8 formed on their surfaces are provided at four locations at the ends and at the center. A diode element 1 is provided on the central insulator 4, and one electrode of the diode element 1 is joined to the metal base 5.

A capacitor (element) 2 is placed on the upper electrode 8 in the figure and connected to an external lead 11, an external lead 14 is connected to the lower electrode 8, and these upper and lower electrodes 8 and the diode 1 are connected to a metal They are connected by thin wire 3. Further, the left and right electrodes 8 are connected to diodes 12 and 13, respectively, and these electrodes 8 and the upper electrode of the capacitor 2 are connected by a thin metal wire 3.

FIG. 3 shows a circuit diagram of an example of a circuit used in the semiconductor device 10 of this embodiment and its equivalent circuit diagram.

The operation will be explained with reference to FIG. First, when the input power becomes sufficiently large and current flows through the PIN diode 1, the resistance of the diode decreases and it can be considered as a short circuit. At this time, if the impedance of the inductance L1 of the thin metal wire 8 connected to the external diode 11 is large, a short circuit will not occur. When a capacitor 2 having a capacitance C1 that causes series resonance with Ll at the signal frequency is inserted in series with Ll, the impedance seen from the input port to the diode becomes short-circuited and is totally reflected.

On the other hand, when the input power is sufficiently small, the PIN diode 1 has a high resistance, and the signal is transmitted from the lines 12 to 13. However, due to the junction capacitance of the diode or the capacitance between the electrodes of the container, the impedance seen from the input port does not become sufficiently high due to this capacitance. Therefore, a part of the signal is not transmitted to the line 13 and flows into the diode element 1 side. To prevent this,
3. Above the inductance in Figure 3. By creating parallel resonance with the capacitance near the diode in the circuit with capacitance C2, high impedance and low loss can be achieved.

Now, if the inductance L1 is 0.2nH, 10G
For a signal frequency of Hz, C1 will be 1.27PF.

Adjustment will be made using the L3 and 02 circuits, but since the fourth external lead 14 is directly connected to the diode 1, it has the advantage of being able to resonate with all capacitance values that enter the vicinity of the diode.

In this embodiment, a PIN diode has been described, but the present invention can also be applied to a switching diode, and it goes without saying that the polarity of the diode can be reversed.

〔Effect of the invention〕

As explained above, the present invention is applicable to conventionally used PI
Characteristics that could not be obtained with just an N diode can now be obtained. In other words, at 10 GHz, isolation was only about 7 dB obtained with a diode alone, but it was improved to 20 dB, and the loss was further reduced to 0.8 dB.
We were able to improve it from dB to 0.4dB.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are a partially cutaway plan view and internal details of an embodiment of the present invention, FIG. 2 is an equivalent circuit diagram of FIG. 1,
3(a) and 3(b) are a circuit diagram and an equivalent circuit diagram of the usage example of FIG. 1, and FIG. 4(a). (b) is a circuit diagram and an equivalent circuit diagram of an example of a conventional limiter circuit. 1... Diode (element), 2... Capacitor (element), 3... Metal thin wire, 4... Insulator, 5... Metal base, 6... Heat sink, 7... Installation screw,
8... Electrode, 10... Semiconductor device, 11-14...
・External lead.

Claims (1)

[Claims] A metal base, a diode element placed on the metal base with the metal base as one electrode, two pairs of insulators placed on the metal base around the diode element, and a diode element placed on the metal base around the diode element, and In a semiconductor device including electrodes disposed on each side and a thin metal wire connecting these electrodes and the diode, two pairs of external leads are connected opposite to the electrodes on the insulator, and one of the two pairs A pair of electrodes are connected to the diode by a thin metal wire, a capacitor having a capacitance that resonates with the inductance of the thin metal wire at the frequency used is mounted on one of the electrodes, and the opposite electrode of this capacitor is connected to the diode. A semiconductor device characterized in that the external lead pair is connected to another electrode pair orthogonal to the external lead pair.