KR940006892B1 - Signal detecting circuit of recording apparatus - Google Patents

Abstract

The circuit comprises a first differential amplifier for inputting reference signal to compare with the appointed input signal and its amplitude, a second differential amplifier for inputting the output of variable direct current source and outputting reference signal in response to input level, a level converter for inputting output of first differential amplifier and changing the input level, and a comparator for inputting and comparing the output of the second differential amplifier and level converter.

Description

Signal detection circuit of recording device

1 is a view showing a conventional signal detection circuit

2 is a view showing a signal detection circuit according to the present invention

3 is a specific embodiment of FIG.

FIG. 3 (a) is a waveform diagram of point a in FIG.

FIG. 3 (b) is a waveform diagram of point b in FIG.

FIG. 3 (c) is a waveform diagram of point c of FIG.

3 (d) is an output waveform diagram of FIG.

The present invention relates to a signal detection circuit of a recording apparatus, and more particularly, to a circuit for comparing an input signal with a set signal and detecting a difference.

Circuits that detect the magnitude of the signal are commonly used in recorders. In order to be able to correspond to all input signal sizes, the signal on the tape is set to the size of a signal that is not saturated, and automatic level recording is performed based on this set signal.

In this regard, a conventional signal detection circuit is shown in FIG. Referring to FIG. 1, the conventional signal detection circuit is composed of a comparator 1 having a non-inverting terminal (+) connected to an input voltage Vi and an inverting terminal (-) connected to a reference voltage VREF. In this conventional circuit, the input voltage and the reference voltage are fixed. However, when looking at the component of Vi as the input voltage, the signal component and the DC bias component are input to Vi. It is well known that the reference voltage VREF of the comparator 1 is fixed. In this state, the DC bias component among the components of the input voltage Vi may change according to the process change or the temperature change. In this case, when the difference between the reference voltage VREF and the DC bias component changes, the output level of the comparator 1 This change will occur. Therefore, there has been a problem that the output voltage of the comparator 1 changes when the DC component of the input voltage Vi is changed according to an external environment.

Accordingly, an object of the present invention is to provide a signal detection circuit capable of generating a stable output voltage even if the DC component of an input signal changes.

In order to achieve the object of the present invention, the present invention provides a signal detection circuit built in the recording apparatus, the first differential amplifier for inputting a predetermined input signal and a reference signal for comparing the magnitude of the input signal, respectively; A second differential amplifier for inputting an output signal of a variable DC power supply and outputting the reference signal in response to the input level, a level converter for inputting an output signal of the first differential amplifier and shifting the input level; Characterized in that it is a signal detection circuit having a comparator for inputting and comparing the output signal of the secondary amplifier and the level converter.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 shows the configuration of the signal detection circuit according to the present invention. Referring to FIG. 2, the signal detection circuit of the present invention includes a first differential amplifier 11 for inputting an input voltage Vi to a non-inverting terminal (+), a non-inverting terminal connected to a reference voltage source VREF, and an inverting terminal (-). The grounded second differential amplifier 12, the level converter 13 receiving the output of the first differential amplifier 11, and the output of the level converter 13 are input to the non-inverting stage and the second differential amplifier It consists of a comparator 14 which inputs the output of (12) to an inversion stage. The output of the second differential amplifier 12 is also input to the inverting end of the first differential amplifier 11. Looking at the characteristics according to the configuration of Figure 2 as follows. As is well known in the art, a voltage source for providing an input bias to an input signal is generally present inside an integrated circuit (IC), and the voltage source is processed similarly to the above input signal. Or change due to temperature. Therefore, as can be seen from the configuration shown in FIG. 2, the reference voltage source VREF as the voltage source for input bias (which operates as a variable DC power supply as its level can be changed according to process or temperature change). When is applied to the comparison voltage of the second differential amplifier 12, the following action occurs. That is, even if the input signal Vi input to the non-inverting terminal of the first differential amplifier 11 is changed by a process or temperature change, the second differential amplifier 12 input to the inverting terminal of the first differential amplifier 11 is changed. By varying the output voltage together, the variation difference between the input signal Vi and the VRER generated in FIG. 1 does not occur. Therefore, in the present invention, the output voltage of the comparator 12 is linked to the input DC fluctuation, thereby solving the problem of fluctuation in the output level due to the unstable input of the input signal.

3 shows a specific embodiment of the present invention according to the configuration of FIG. Referring to FIG. 3, transistors Q1, Q2, Q3, Q4, Q5 and current source I1 form the first differential amplifier 11 of FIG. Transistors Q6, Q7, Q8, Q9 and current source I2 constitute second differential amplifier 12 of FIG. The transistor Q12 and the resistor R2 and the current source I4 constitute the level converter 13 of FIG. Transistors Q10, Q11, resistor R1, and current source I3 form comparator 14 in FIG. In the first differential amplifier 11, the node B connected to the collector of transistor Q4 becomes an output terminal and is connected to the base of transistor Q12 of level converter 13. In the second differential amplifier 12, the collector of the transistor Q7 becomes an output terminal and is connected to the base of the transistor Q2 of the first differential amplifier 11 and the transistor Q10 of the comparator 14. The node C connected to the base of the transistor Q11 in the comparator 14 becomes the input terminal to the non-inverting terminal.

3 (a) (b) (c) (d) are respectively connected to the signal input terminal A and the output terminal B of the first differential amplifier 11 (or the collector of the transistor Q4) in FIG. Waveform at the connected node), the output terminal C of the level converter 13 (or the node connected to the base of the transistor Q11) and the output terminal D of the comparator 14 (or the node connected to the collector of the transistor Q11). Shows.

Referring to the third (a) (b) (c) (d) the operation characteristics of the signal detection circuit according to the present invention will be described as follows. The output of the second differential amplifier 12 input to the inverting end of the first differential amplifier 11 becomes the reference voltage VREF having a positive level. As described above, the VREF operates by a variable DC power supply. For example, even if the input signal is changed by a process or a temperature, the VREF is also changed by the same, thereby eliminating the instability of the detection signal caused by the change of the input signal. Therefore, in the first differential amplifier 11, a stable bias is maintained by a positive reference voltage input from the second differential amplifier I2 to the inverting stage, and thus the input voltage Vi (see also third (a)) is applied. Output only a positive voltage (see also third (b)). Here, since the level of the output voltage of the first differential amplifier 11 and the output voltage of the second differential amplifier 12 are the same, in order to set the magnitude of the signal to be detected through the comparator 14, The output of the secondary amplifier 12 is applied directly to the non-inverting end of the comparator 14 and the output of the second differential amplifier 11 is applied to the level converter 13. In the level converter 13, the input of the inputted first differential amplifier 11 is dropped through the base-emitter voltage of the transistor Q12 and the resistor R2 (the third (c) is also true). The non-inverting end of the comparator 14 is supplied. Then, the comparator 14 compares the waveform of FIG. 3 (c) whose level is converted with the reference voltage waveform which is the output waveform of the second differential amplifier 12 to detect a signal having the same level as that of FIG. become. In other words, the level converter 13 is a means for setting the size of the signal to be detected, it can be seen that the second differential amplifier 12 is a means for canceling the DC variable of the input voltage.

Therefore, it will be possible to those skilled in the art that other embodiments that can achieve the object of the present invention can be made even if the circuit configuration shown in FIG.

As described above, the present invention has an effect that a stable detection signal can be obtained by removing an unstable direct current component included in the signal even when an input signal is input to a recording device or the like.

Claims (1)

A signal detection circuit built in a recording apparatus, comprising: a first differential amplifier for inputting a predetermined input signal and a reference signal for comparing the magnitude of the input signal, and an output signal of a variable DC power supply and input to this input level; A second differential amplifier for outputting the reference signal in response, a level converter for inputting an output signal of the first differential amplifier and varying the input level, and a respective output signal of the second differential amplifier and the level converter; And a comparator for comparing and outputting the comparator.