JPH04223706A - Input terminal circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for terminating an input portion of a logic circuit or an amplifier circuit, and further relates to an IC in which an amplifier circuit and a logic circuit using the input termination circuit are integrated.

0002

2. Description of the Related Art One type of input circuit for a conventional logic circuit or amplifier circuit is shown in FIG. The signal from the input section passes through the coupling capacitor C3 and is terminated by the terminating resistor RT3 through the DC bias VBIN. The high frequency signal is input to the base terminal of the transistor T4 and output from the emitter terminal. Transistor T5 is a constant current source transistor, and resistor RE
2 is a protective resistor for preventing excessive current from flowing.

FIG. 4 shows another type of conventional input circuit. The format shown in FIG. 4 is called the collector open format. The output circuit of the logic circuit or amplifier circuit in the previous stage is composed of two pairs of transistors T6 and T7 having a common emitter, a constant current source transistor T8, and a protection resistor RE3. The input circuit includes a terminating resistor RT4 and a transistor T.
9 and constant current source transistor T10 and protective resistor RE4
It consists of In the actual circuit, the collector terminal of the transistor T6 or T7 in the output circuit is connected to the base terminal of the transistor T9 in the input circuit.

0004

The circuit of FIG. 3 is primarily used for silicon bipolar transistors. In this case, since the voltage between the base and emitter of transistor T4 was small, by applying DC voltage VBIN, which has a potential higher than GND, to the other end of terminating resistor RT3, the voltage between the emitter and collector remains constant even if the voltage is changed. It was necessary to operate the transistor T4 in the non-saturation region where the collector current flows. In addition, in the circuit of FIG. 4, by supplying current from the output circuit with the collector open to the terminal resistor RT4, the DC level of the base terminal input to the transistor T9 is adjusted.
It was necessary to operate it in the non-saturated region. Figure 3,
4, GND is the ground, and VEE is the power supply voltage, for example, -5.2V.

An object of the present invention is to increase the base-emitter voltage by using a heterojunction bipolar transistor as the transistor, thereby simplifying the input circuit and expanding the dynamic range of the input signal.

[0006]

[Means for Solving the Problems] In order to achieve the above object of the present invention, a heterojunction bipolar transistor is used as a device applied to a circuit, a terminating resistor is connected between the base and collector of the input transistor, and a terminating resistor is connected to the base of the input transistor. Added capacity.

[0007]

[Operation] According to this configuration, the input can be terminated by inserting a terminating resistor between the base and collector of the input transistor, and there is no need to add a capacitor to match the DC level with the previous stage circuit. , the input circuit can be simplified. In addition, in the input transistor of the input termination circuit according to the present invention, the base-emitter voltage becomes the emitter-collector voltage as it is, so the base-emitter voltage is about 1.5V, compared to 0.8V of a silicon bipolar transistor. When a large heterojunction bipolar transistor is used, it is possible to maintain an emitter-collector voltage of about 1.5V, and the transistor can be operated in a non-saturation region where a constant collector current flows even if the emitter-collector voltage is changed.

[0008]

EXAMPLES Examples of the present invention will be described in detail below.

FIG. 1 shows an embodiment according to the present invention. First, an input signal passes through a coupling capacitor C1 and is terminated at a terminating resistor RT1. Furthermore, reaching the base of transistor T1,
It is output from the emitter of transistor T1. Transistors T1 and T2 use heterojunction bipolar transistors, so the base-emitter voltage is 1.5.
It is possible to operate the transistor T1 in a non-saturated region even if the termination resistor RT1 is grounded. Here, I1 indicates a constant current source.

FIG. 2 is a diagram showing FIG. 1 in more detail. The constant current source I1 in FIG. 1 is the transistor T3.
and is replaced by the protective resistor RE1.

[0011]

[Effects of the Invention] As described above, according to the present invention, the input circuit can be simplified by connecting a terminating resistor to the collector/base terminal of the input transistor in the input portion of the logic circuit or amplifier circuit. can. Furthermore, since a heterojunction bipolar transistor is used as the transistor, the base-emitter voltage is as high as about 1.5V, and the dynamic range of the input signal can be widened. 5 and 6 show the characteristics when a heterojunction bipolar transistor and a silicon bipolar transistor are applied to the circuit shown in FIG. 2. For input voltage,
Comparing the regions where the output voltage is linear, it can be seen that the silicon bipolar transistor in FIG. 6 has a linear output voltage of 0.8V, and the heterojunction bipolar transistor in FIG. 5 has a linear output voltage of 1.34V, indicating that the heterojunction bipolar transistor is superior. Since the input circuit can be simplified and the dynamic range of the input signal can be widened, the number of input circuit elements that greatly affect the characteristics of the logic circuit or amplifier can be minimized, and variations in circuit performance due to element variations can be suppressed. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a circuit diagram showing one embodiment of the present invention.

FIG. 3 is a circuit diagram showing an input portion of a conventional logic circuit or amplifier circuit.

FIG. 4 is a circuit diagram showing an input portion of a conventional logic circuit or amplifier circuit.

FIG. 5 is a characteristic diagram showing the operating principle of the present invention.

FIG. 6 is a characteristic diagram showing the operating principle of the present invention.

[Explanation of symbols]

T1 to T10...Transistor, RT1 to RT4...Terminal resistor, RE1 to RE4...Protection resistor, C1 to C3...Coupling capacitance, I1...Constant current source, IN...Input terminal, OUT...Output terminal, GND...Grounding terminal, VEE... Power terminal, OUT1, O
UT2...Collector open output terminal, VBIN...GND
Higher potential DC terminal.

Claims (11)

[Claims] Claim 1: A transistor having one end of a capacitor connected to an input terminal, the other end of the capacitor as a base, a resistor as a base and collector, and a constant current source as an emitter, with the emitter as an output point. An input termination circuit characterized by: 2. An emitter follower having one end of a capacitor connected to the input terminal, the other end of the capacitor as a base, and a resistor connected to the base and collector, and a constant current source connected to the emitter. The input termination circuit according to claim 1. 3. The input termination circuit according to claim 2, wherein an NPN transistor or a PNP transistor is used as the emitter follower. 4. The input termination circuit according to claim 1, wherein a transistor is used between the collector and emitter, which becomes unsaturated when a base-emitter voltage and half of the input signal voltage are applied. 5. The input termination circuit according to claim 1, wherein the transistor is a heterojunction bipolar transistor. 6. The input termination circuit according to claim 1, wherein the constant current source comprises a series connection of a transistor and a resistor, or a transistor or a resistor. 7. The input termination circuit according to claim 1, wherein the collector terminal of the transistor is grounded. 8. An amplifier circuit using the input termination circuit according to claim 1. 9. The amplifier circuit according to claim 8, wherein a resistor and a transistor excluding a capacitance in the input termination circuit are integrated. 10. A logic circuit using the input termination circuit according to claim 1. 11. The logic circuit IC according to claim 10, wherein a resistor and a transistor excluding a capacitance in the input termination circuit are integrated.