JPH09252222A - Wide band amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To apply an amplifier even in a high frequency range and also to amplify the signals of various levels up to large electric power by using an electrostatic induction transistor that excels in the frequency characteristic as a cascade connection circuit. SOLUTION: In a cascade connection circuit, a gate grounded circuit of a SIT(electrostatic induction transistor) is connected to the next stage of a source grounded circuit. In such a constitution, the negative bias is applied to the gate of the SIT of the preceding stage to secure the OFF characteristic for an entire circuit due to the normally ON characteristic of the SIT. The negative bias value is effective at about -5V. At the same time, another cascade connection circuit where a gate grounded circuit of the SIT is connected to the next stage of a source grounded circuit of an FET(field effect transistor) is also available. In such cases, the normally ON characteristic is secured for an entire circuit with use of the FET and no negative bias is needed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a static induction transistor (hereinafter referred to as "SIT") as an amplifying element to obtain a high amplification degree over a wide frequency range, and a cascade connection circuit and a wide band amplifier. Regarding

[0002]

2. Description of the Related Art Recently, as the definition of a display such as a CRT (cathode ray tube) has become higher and higher, a broadband and high breakdown voltage amplifier is required. In addition, since the signal amplification of the optical electric field sensor also includes frequency components in a wide band, a wide band amplifier is required.

FIG. 4 shows a conventional cascade junction transistor using a bipolar junction transistor (hereinafter referred to as BJT). In this circuit, two transistors of the same type (NPN type in the example of FIG. 4) are used. The transistor in the front stage receives the input signal and amplifies the current, and the transistor in the rear stage has a voltage amplifying function.

[0004]

However, the frequency characteristics of BJTs and field effect transistors (hereinafter referred to as FETs) used in conventional solid-state wide band amplifiers are already limited to their requirements. BJTs that can amplify up to several GHz at low signal levels are commercially available, but there are problems such as being unsuitable for power amplification. There is an inverse correlation between the frequency and power of the signal to be handled, and CRT
It can be said that BJT is reaching its limit for such applications. In addition, the optical electric field sensor needs to amplify signals of wide frequencies and various magnitudes, and particularly requires an amplifier with a wide band.

The present invention aims to remedy the above-mentioned drawbacks of BJTs and FETs.

[0006]

In order to solve the above-mentioned problems, the present invention uses SIT having excellent frequency characteristics as a cascade connection circuit as a wide band amplifier. That is, it is a wide band amplifier characterized in that it is configured by a cascade connection circuit in which a gate ground circuit of the SIT is connected to a stage subsequent to the source ground circuit of the SIT. A wide band amplifier comprising a cascade connection circuit in which a grounded gate circuit of an induction transistor is connected, and a wide band using a wide band amplifier configured by the cascade connection circuit described in any one of the above and It is a video amplifier.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to examples.

FIG. 1 shows a cascade amplifier using a normally-on type SIT. Since the SIT has a normally-on characteristic, it is necessary to apply a negative bias to the gate of the SIT in the preceding stage so that the entire circuit has an off characteristic, but the negative bias value may be about -5V.

In FIG. 2, an FET (enhancement mode FET such as MOS type) is used in the preceding stage. By using the FET, the entire circuit has a normally-off characteristic and no negative bias is required.

FIG. 3 shows a wideband video amplifier circuit for CRT in which the cascade connection circuit and the buffer circuit shown in FIG. 1 are combined. G (grid) -K which is the input terminal of CRT
Since the capacity between the (cathode) is about several PF to 10 PF, a considerable amount of charge / discharge energy is required. For this reason,
A buffer circuit is required, and this CIT wide-band video amplifier for CRT uses SIT with good complementary characteristics as a complementary transistor for buffer (complementary NPN type and PNP type). Could be supplied.

[0011]

The wide band amplifier of the present invention can be used up to a high frequency range and can amplify a large power even for signals of various sizes.

Particularly, as a problem of the conventional circuit, since the complementary characteristics of BJT are unbalanced, when used as a CRT video amplifier in which an image is distorted, color unevenness occurs, or a black line becomes white, complementary Compared to BJT, which has poor characteristics, SIT has better frequency characteristics, so it can supply a large current without distortion to the load, and can significantly improve color misregistration and sharpness of characters, which was difficult to correct in the past. Became.

[Brief description of drawings]

FIG. 1 is a diagram showing a circuit configuration of a cascade amplifier configured by SIT.

FIG. 2 is a diagram showing a circuit configuration of a cascade amplifier including a front stage FET and a rear stage SIT.

FIG. 3 is a diagram showing a circuit configuration of a CRT wideband video amplifier configured by SIT.

FIG. 4 is a diagram showing a circuit configuration of a conventional BJT cascade amplifier.

Claims (3)

[Claims] 1. A wide band amplifier comprising a cascade connection circuit in which a grounded gate circuit of the static induction transistor is connected to a stage subsequent to a grounded source circuit of the static induction transistor. 2. A wide band amplifier comprising a cascade connection circuit in which a grounded gate circuit of a static induction transistor is connected to a subsequent stage of a grounded source circuit of a field effect transistor. 3. A wideband video amplifier using a wideband amplifier composed of the cascade connection circuit according to claim 1. Description: