JPS62109A - Amplifier - Google Patents

Abstract

PURPOSE:To output accurately only a pulse signal while the fluctuation of an operational amplifier is cancelled by allowing both plus and minus sides of the operational amplifier to be fluctuated even when the DC voltage is fluctuated. CONSTITUTION:A signal outputted from an emitter of a transistor (TR) 12 is inputted directly to a plus side input terminal of the operational amplifier 16 on one hand and also inputted to a minus side input terminal of the operational amplifier 16 via a low pass filter comprising a resistor 14 and a capacitor 15 on the other hand. The operational amplifier 16 amplifies a difference between a DC voltage including a pulse signal and a DC voltage eliminated with the pulse signal by the low pass filter, that is, the pulse signal and the result is outputted from output terminals 17, 18. Even when the DC voltage is fluctuated due to a cause such as dissidence of impedance matching, both the plus side input terminal and the minus side input terminal of the operational amplifier 16 are fluctuated similarly. Thus, only the pulse signal is outputted from the output terminal 17, 18 independently of the fluctuation of the DC voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an amplifier device used in a device for remotely transmitting a pulse signal superimposed on a direct current voltage.

Conventional Technology Conventionally, when a pulse signal superimposed on a DC voltage is amplified by removing the DC voltage, the signal input to the input terminal 1 is first received by the high impedance emitter follower of the transistor 2, as shown in Fig. 2. , a resistor 3 and a capacitor 4 remove direct current, and an operational amplifier 5 amplifies only the pulse signal, which is output from an output terminal 6.7.

Problems to be Solved by the Invention However, as high-speed transmission advances, multiple terminals are connected on a coaxial cable terminated with a terminating resistor, and data can be transmitted and transmitted between any two points. , the number of cases where data is received will increase. In this case, as the distance from the transmitter increases, the information transmitted to the receiver attenuates in proportion to the distance, so the pulse information superimposed on the DC level centered on the pulse peak value 172 is reproduced. -Needs to be restored.

For this reason, an AC amplifier as shown in Figure 2 was used to cut the DC level and amplify only the signal component, but due to the high frequency, the signal system was transmitted with an impedance of 50Ω or 75Ω. As a result, impedance on the drive side cannot be made high, and impedance matching may not be achieved between the transmitter and the receiver, and fluctuations in the DC voltage are output as noise, creating a problem.

SUMMARY OF THE INVENTION In order to solve these conventional problems, it is an object of the present invention to provide an excellent amplifier device that has a simple circuit configuration and can perform impedance matching between transmitting and receiving signals.

Means for Solving the Problems In order to solve the above problems, the present invention receives an input signal with a high impedance emitter follower, inputs one of the signals of the emitter follower directly to the positive side of an operational amplifier, and inputs the other signal to the positive side of an operational amplifier. It is configured to be input to the minus side of an operational amplifier via a low-pass filter.

According to the present invention, with the above configuration, even if the DC voltage fluctuates, both the positive side and the negative side of the operational amplifier fluctuate.
This DC voltage fluctuation is canceled out to the output of the operational amplifier, so that only the pulse signal is accurately output.

Embodiment FIG. 1 is a circuit diagram of an amplifier device in an embodiment of the present invention. In FIG. 1, 11 is an input terminal, 12 is a transistor forming an emitter follower with a bias resistor 13, 14 is a resistor that forms a low-pass filter together with a capacitor 15, 16 is an operational amplifier, and 17 and 18 are output terminals.

When a pulse signal superimposed on a DC voltage is input to the input terminal 11, it is received at high impedance by an emitter follower composed of a transistor 12 and a resistor 13. One side of the signal output from the emitter of the transistor 12 is directly input to the positive side input terminal of the operational amplifier 16, and the other side is inputted to the negative side input terminal of the operational amplifier 16 via a low-pass filter composed of a resistor 14 and a capacitor 15. is input. The operational amplifier 16 amplifies the difference between the DC voltage containing the pulse signal and the DC voltage from which the pulse signal has been removed by the low-pass filter, that is, the pulse signal, and outputs it from output terminals 17 and 18.

Even if the DC voltage fluctuates due to impedance matching mismatch or other reasons, the operational amplifier 1
Since both the positive terminal and the negative terminal of 6 fluctuate in the same way, only the pulse signal is accurately sent out from the output terminals 17 and 18 without being affected by fluctuations in the DC voltage.

Effects of the Invention As is clear from the embodiments described above, the present invention receives an input signal by a high-impedance emitter follower, then directly inputs one of the signals of the emitter follower to the positive side of an operational amplifier, and sends the other signal through a low-pass filter. Since the configuration is such that the input is applied to the negative side of the operational amplifier, even if the DC voltage fluctuates, both the positive and negative sides of the operational amplifier will fluctuate, and this DC voltage fluctuation will be canceled out in the output of the operational amplifier. This has the effect that only the pulse signal is accurately output.

[Brief explanation of drawings]

Resistor, 14... Resistor, 15... Capacitor, 16... Operational amplifier, 17.18...
...Output terminal.

Claims (1)

[Claims] An emitter follower circuit inputs a superimposed signal of DC voltage and high frequency pulse sent from a low impedance transmission system, a signal from this emitter follower circuit is directly input to the positive input terminal, and a signal from the emitter follower circuit is passed through a low pass filter. and an operational amplifier that inputs to the negative side input terminal.