JP2006217334A - Fm demodulation circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain linearity of precise f-V property through a wide frequency area of an input FM signal. <P>SOLUTION: This FM demodulation circuit comprises: an edge detection means which detects an edge of the input FM signal of a differential format and outputs the detected result by using the differential format; a differential amplifier 3 where only one of a positive phase input terminal and an opposite phase input terminal is connected with a positive phase output terminal or an opposite phase output terminal of the edge detection means; and a reference voltage generation circuit 4 which applies reference voltage to an input terminal which is not connected with the output terminal of the edge detection means among the positive phase input terminal and an opposite phase input terminal of the differential amplifier 3. The edge detection means comprises: a differential delay circuit 1 outputting a signal obtained by delaying the input FM signal; and a differential AND circuit 2 which inputs the input FM signal as first input and a signal outputted from the differential delay circuit as second input. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a broadband FM (Frequency Modulation) demodulation circuit that operates with high accuracy.

  An example of a conventional FM demodulation circuit is shown in FIG. 7 (see, for example, Patent Document 1 and Non-Patent Document 1). The conventional FM demodulation circuit has a differential delay circuit 1 that receives a positive phase input signal INP and a negative phase input signal INN, a differential AND circuit 2, and a positive phase output signal cp of the differential AND circuit 2. It comprises a differential amplifier 3 that receives the phase output signal cn. The actual demodulated output of the FM demodulating circuit is obtained by connecting a low-pass filter (not shown) to the positive phase output signal O3P of the differential amplifier 3.

  The connection of the conventional FM demodulation circuit will be described. The positive phase input signal INP is input to the positive phase input terminal of the differential delay circuit 1 and the first positive phase input terminal ap of the differential AND circuit 2, and the negative phase input signal INN is the reverse of the differential delay circuit 1. The phase input terminal and the first negative phase input terminal an of the differential AND circuit 2 are input. The positive phase output signal of the differential delay circuit 1 is input to the second positive phase input terminal bp of the differential AND circuit 2, and the negative phase output signal of the differential delay circuit 1 is the second phase output signal of the differential AND circuit 2. Are input to the negative phase input terminal bn. The positive phase output terminal cp of the differential AND circuit 2 is connected to the positive phase input terminal of the differential amplifier 3, and the negative phase output terminal cn of the differential AND circuit 2 is connected to the negative phase input terminal of the differential amplifier 3. Is done. The outputs of the differential amplifier 3 are a normal phase output signal O3P and an inverted output signal O3N.

  The operation of the conventional FM demodulation circuit will be described with reference to FIG. A normal phase input signal INP and a negative phase input signal INN which are FM signals are input to the FM demodulation circuit of FIG. 8A and 8B, the positive phase input signal INP and the negative phase input signal INN after the sine wave of the frequency f, which is the fundamental wave of the FM signal, is converted into a pulse of the frequency f by the amplifier. Is shown. The normal phase input signal INP and the negative phase input signal INN are both delayed by a delay time τ by passing through the differential delay circuit 1. A positive phase input signal INP and a negative phase input signal INN are input to the first positive phase input terminal ap and the first negative phase input terminal an of the differential AND circuit 2, respectively. The positive phase output signal and the negative phase output signal of the differential delay circuit 1 are input to the positive phase input terminal bp and the second negative phase input terminal bn, respectively (FIGS. 8A to 8D). ).

  The differential AND circuit 2 is a logical product of the inputs of the first positive phase input terminal ap and the first negative phase input terminal an and the inputs of the second positive phase input terminal bp and the second negative phase input terminal bn. Take. As a result, as shown in FIGS. 8E and 8F, the positive phase input signal INP rises from low to high at the positive phase output terminal cp and the negative phase output terminal cn of the differential AND circuit 2. A pulse is generated at the timing. This pulse has a pulse width of about the delay time τ of the differential delay circuit 1. The pulses output from the positive phase output terminal cp and the negative phase output terminal cn of the differential AND circuit 2 are differentially amplified by the differential amplifier 3 and output as a normal phase output signal O3P and an inverted output signal O3N (FIG. 8 (G), FIG. 8 (H))). The normal phase output signal O3P is time-integrated by a low-pass filter (not shown) and becomes an output signal of the FM demodulation circuit. That is, charge is accumulated in the capacitance of the low-pass filter for the time of the pulse width of the positive phase output signal O3P, and is output as the voltage Vo.

  If the frequency f of the FM signal (the positive phase input signal INP and the negative phase input signal INN) increases, the number of pulses per unit time of the positive phase output signal O3P increases, so the output voltage Vo increases and the frequency f If it becomes lower, the number of pulses per unit time of the positive phase output signal O3P becomes smaller, so the output voltage Vo becomes lower. Therefore, the frequency level of the FM signal is converted into the potential level, and the FM signal is demodulated into an AM signal. In order to perform FM demodulation with less distortion, the output voltage Vo is proportional to the frequency f with high accuracy over a wide range of the frequency f of the FM signal (hereinafter referred to as linearity of the fV characteristic). It is essential. When the output pulse area of the positive phase output signal O3P shown in FIG. 8G is invariant over a wide frequency and the noise appearing at signal portions other than the output pulse is small, the fV characteristic has good linearity. Achieved.

The applicant has not yet found prior art documents related to the present invention by the time of filing other than the prior art documents specified by the prior art document information described in this specification.
JP 2002-368542 A Hirose, Kishine, Ishihara, Akazawa, Kikushima, Kishimoto, Kumozaki, "High gain, wideband FM demodulation IC for optical video transmission by AM / FM batch conversion", IEICE Technical Report CAS 96-115, March 1997 , P. 111-117

  The problem with the conventional FM demodulator circuit shown in FIG. 7 is that the differential amplifier 3 is caused by an error in the pulse width and noise generated at both the positive phase output terminal cp and the negative phase output terminal cn of the differential AND circuit 2. Since it is input, high-precision linearity of the fV characteristic cannot be obtained. Thus, the conventional FM demodulation circuit cannot obtain an FM demodulation characteristic with little distortion over a wide input frequency region. Here, the circuit configuration of the differential AND circuit 2 is shown in FIG. In FIG. 9, Q1 to Q9 are N channel MOS transistors, I1 to I3 are constant current sources, and R1 and R2 are resistors. In the differential AND circuit 2, as illustrated in FIG. 9, there is no symmetry between a circuit configuration for generating a signal output to the positive phase output terminal cp and a circuit configuration for generating a signal output to the negative phase output terminal cn. . Therefore, there is a difference in response characteristics and noise peak value between the signal output to the positive phase output terminal cp and the signal output to the negative phase output terminal cn. If the response characteristics are different, the output pulse width may be different from τ with respect to the delay difference τ between the first input and the second input of the differential AND circuit 2.

  The positive-phase output signal O3P of the differential amplifier 3 is affected by the signal having the wider pulse width of the signal output to the positive-phase output terminal cp and the signal output to the negative-phase output terminal cn. Becomes wider than τ, and noise appearing at both the positive phase output terminal cp and the negative phase output terminal cn is superimposed. As described above, when the output pulse width of the positive phase output signal O3P is wide, when the frequency f of the input FM signal is high, the tail portions of adjacent pulses overlap, and the area of the output pulse is lower than that in the case of the low frequency. Get smaller. The noise superimposed on the positive phase output signal O3P changes the peak value of the output pulse due to the phase relationship with the next output pulse adjacent to the noise. Such a change in the width and peak value of the output pulse of the positive phase output signal O3P results in a change in the area of the output pulse depending on the frequency f of the input FM signal, and the linearity of the output voltage Vo of the low-pass filter with respect to the frequency f is changed. To lose. As described above, the conventional FM demodulation circuit has a problem that it is impossible to achieve highly accurate fV linearity over a wide frequency range of the input FM signal.

  The present invention has been made to solve the above-described problem, and an object of the present invention is to provide an FM demodulation circuit capable of realizing highly accurate linearity of fV characteristics over a wide frequency range of an input FM signal. To do.

The FM demodulating circuit of the present invention detects an edge of a differential input FM signal and outputs the detection result in a differential format, and only one of a positive phase input terminal and a negative phase input terminal. Differential amplification means connected to the positive phase output terminal or the negative phase output terminal of the edge detection means, and the output terminal of the edge detection means among the positive phase input terminal and the negative phase input terminal of the differential amplification means And a reference voltage generating circuit for applying a reference voltage to the input terminal not connected to the input terminal.
Further, in one configuration example of the FM demodulation circuit of the present invention, the edge detection means includes a differential delay circuit that outputs a differential signal obtained by delaying the differential input FM signal, and the differential signal. The input FM signal is the first input, the differential signal output from the differential delay circuit is the second input, and the result of the logical product of the first input and the second input is obtained. It comprises a differential AND circuit that outputs in a differential format.
Further, in one configuration example of the FM demodulation circuit of the present invention, the edge detection means includes a differential delay circuit that outputs a differential signal obtained by delaying the differential input FM signal, and the differential signal. Input FM signal as a first input, a differential signal output from the differential delay circuit as a second input, and an exclusive OR of the first input and the second input It comprises a differential EXOR circuit that outputs the result in a differential format.
In addition, one configuration example of the FM demodulating circuit according to the present invention further includes an output terminal that is not connected to an input terminal of the differential amplifying means, out of a positive phase output terminal and a negative phase output terminal of the edge detecting means. And a load circuit connected to the.

  According to the present invention, only one of the positive phase output and the negative phase output of the edge detection means is connected to the differential amplification means, and a reference voltage is applied to a terminal to which the differential amplification means is not connected. Since only one of the positive-phase and negative-phase outputs of the edge detection means that has good response characteristics and low noise can be used, differential amplification accompanying an increase in the frequency of the input FM signal The increase and decrease of the pulse width of the output pulse of the means can be suppressed, and the noise appearing at the output of the differential amplifying means can be reduced. Thereby, in this invention, the area of the output pulse of a differential amplification means is made invariable over the wide frequency band of an input FM signal, and the highly accurate linearity of fV characteristic is realizable. Therefore, it is possible to provide an FM demodulating circuit having low distortion over a wide frequency band of the input FM signal. In the present invention, the output pulse width of the differential amplifying means can be adjusted by adjusting the reference voltage applied to the differential amplifying means. As a result, the FM demodulation gain can be adjusted.

  The FM demodulator circuit of the present invention connects only one of the positive and negative phase outputs of the differential AND circuit or the differential EXOR circuit to the differential amplifier with a good response characteristic and low noise. A reference voltage is supplied to a terminal to which the dynamic amplifier is not connected.

[First Embodiment]
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an FM demodulation circuit according to the first embodiment of the present invention. The FM demodulation circuit of the present embodiment includes a differential delay circuit 1 that receives a positive phase input signal INP and a negative phase input signal INN, a differential AND circuit 2, and a reference voltage generation circuit that generates a reference voltage dp. 4 and a differential amplifier 3 that receives the reference voltage dp and the negative phase output signal cn of the differential AND circuit 2 as inputs. The actual demodulated output of the FM demodulator circuit is obtained by connecting a low-pass filter (not shown) to the positive phase output signal O1P of the differential amplifier 3.

  Connection of the FM demodulation circuit of this embodiment will be described. The positive phase input signal INP is input to the positive phase input terminal of the differential delay circuit 1 and the first positive phase input terminal ap of the differential AND circuit 2, and the negative phase input signal INN is the reverse of the differential delay circuit 1. The phase input terminal and the first negative phase input terminal an of the differential AND circuit 2 are input. The positive phase output signal of the differential delay circuit 1 is input to the second positive phase input terminal bp of the differential AND circuit 2, and the negative phase output signal of the differential delay circuit 1 is the second phase output signal of the differential AND circuit 2. Are input to the negative phase input terminal bn. The positive phase output terminal cp of the differential AND circuit 2 is not connected anywhere, and the negative phase output terminal cn of the differential AND circuit 2 is connected to the negative phase input terminal of the differential amplifier 3. The output terminal of the reference voltage generation circuit 4 is connected to the positive phase input terminal of the differential amplifier 3. The outputs of the differential amplifier 3 are a normal phase output signal O1P and an inverted output signal O1N.

  The operation of the FM demodulation circuit according to this embodiment will be described with reference to FIG. A normal phase input signal INP and a negative phase input signal INN, which are FM signals, are input to the FM demodulation circuit of FIG. 2A and 2B, the positive-phase input signal INP and the negative-phase input signal INN after the sine wave of the frequency f, which is the fundamental wave of the FM signal, is converted into a pulse of the frequency f by the amplifier. Is shown. The normal phase input signal INP and the negative phase input signal INN are both delayed by a delay time τ by passing through the differential delay circuit 1. A positive phase input signal INP and a negative phase input signal INN are input to the first positive phase input terminal ap and the first negative phase input terminal an of the differential AND circuit 2, respectively. The positive phase output signal and the negative phase output signal of the differential delay circuit 1 are input to the positive phase input terminal bp and the second negative phase input terminal bn, respectively (FIGS. 2A to 2D). ).

  The differential AND circuit 2 includes a first input (signal input to the first positive phase input terminal ap and the first negative phase input terminal an) and a second input (second positive phase input terminal bp and Logical product with the second negative phase input terminal bn). As a result, as shown in FIG. 2E, a pulse is generated at the negative phase output terminal cn of the differential AND circuit 2 at the timing when the positive phase input signal INP rises from low to high. This pulse has a pulse width of about the delay time τ of the differential delay circuit 1. The pulse output from the negative phase output terminal cn of the differential AND circuit 2 is input to the differential amplifier 3.

  The differential amplifier 3 performs high / low determination of the signal at the negative phase output terminal cn using the reference voltage dp output from the reference voltage generation circuit 4 as a threshold value, amplifies the pulse, and FIG. It outputs as the positive phase output signal O1P and the inverted output signal O1N shown in FIG. 2G (that is, the differential amplifier 3 amplifies the difference between the reference voltage dp and the signal at the negative phase output terminal cn). The normal phase output signal O1P is time-integrated by a low-pass filter (not shown) and becomes an output signal of the FM demodulation circuit. That is, electric charges are accumulated in the capacitance of the low-pass filter for the time of the pulse width of the positive phase output signal O1P and output as the voltage Vo.

  If the frequency f of the FM signal (the positive phase input signal INP and the negative phase input signal INN) increases, the number of pulses per unit time of the positive phase output signal O1P increases, so the output voltage Vo increases and the frequency f If it becomes lower, the number of pulses per unit time of the positive phase output signal O1P becomes smaller, so the output voltage Vo becomes lower. Therefore, the frequency level of the FM signal is converted into the potential level, and the FM signal is demodulated into an AM signal.

  Here, of the positive-phase output and the negative-phase output of the differential AND circuit 2, the signal output to the positive-phase output terminal cp is inferior in response characteristics, and the noise peak value is high. Therefore, in the present embodiment, the positive phase output terminal cp is not connected to the input terminal of the differential amplifier 3, and only the negative phase output terminal cn of the differential AND circuit 2 is connected to the negative phase input terminal of the differential amplifier 3. To do. Thereby, it can avoid receiving the influence of the signal of the positive phase output terminal cp. Therefore, the pulse width of the positive phase output signal O1P is kept narrow and close to the delay time τ of the differential delay circuit 1, and noise other than the pulse appearing in the positive phase output signal O1P is reduced. Since the output pulse area of the positive phase output signal O1P shown in FIG. 2 (F) is invariant over a wide frequency and the noise appearing at a signal location other than the output pulse is small, the fV characteristic of the input FM signal is high up to the high frequency. Good linearity is obtained. Therefore, according to the present embodiment, it is possible to perform FM demodulation with less distortion over a wide range of the frequency f of the FM signal input to the FM demodulation circuit.

FIG. 3 shows the fV characteristics of the FM demodulation circuit of the present embodiment and the conventional FM demodulation circuit shown in FIG. The horizontal axis in FIG. 3 is the frequency f of the input FM signal, and the vertical axis is the error (the deviation from the fV linearity) between the voltage to be output in proportion to the frequency f and the voltage actually output from the FM demodulation circuit. ). fV0 is the fV characteristic of the conventional FM demodulation circuit, and fV1 is the fV characteristic of the FM demodulation circuit of the present embodiment. Here, when a certain frequency f is actually converted into the voltage Vreal by the circuit, the linear approximation line (ideal voltage Video that should be output in proportion to the frequency f) is set as a slope C [mV / MHz]. It is calculated as follows:
Video = C · f (1)
The frequency-voltage conversion error on the vertical axis in FIG. 3 is the difference (Vreal-Video) between the ideal voltage and the actual voltage.
According to this embodiment, when the frequency f of the input FM signal is 1 GHz to 4 GHz, the error of the output voltage Vo can be reduced to about 1/10 of the conventional one. Furthermore, according to the present embodiment, even when the frequency f of the input FM signal is higher than 4 GHz, a large error as in the conventional case does not occur. Therefore, this embodiment has a tremendous effect that enables FM demodulation with remarkably low distortion over a wide range of the frequency f of the input FM signal.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 4 is a block diagram showing a configuration of an FM demodulator circuit according to the second embodiment of the present invention. The same components as those in FIG. 1 are denoted by the same reference numerals. The FM demodulator circuit of the present embodiment inputs the differential AND circuit 2 of the first embodiment to a first input (a first positive phase input terminal ap and a first negative phase input terminal an). Signal) and a second input (a signal input to the second positive-phase input terminal bp and the second negative-phase input terminal bn) is replaced with a differential EXOR circuit 5 that takes an exclusive OR. . As in the first embodiment, the positive phase output terminal ep of the differential EXOR circuit 5 is not connected anywhere and is opened, and only the negative phase output terminal en of the differential EXOR circuit 5 is connected to the differential amplifier 3. Connect to the negative phase input terminal.

  The operation of the FM demodulation circuit according to this embodiment will be described with reference to FIG. As shown in FIG. 5E, the differential EXOR circuit 5 outputs a pulse to the negative phase output terminal en at the timing when the positive phase input signal INP rises from low to high and at the timing when the positive phase input signal INP falls from high to low. The time width of this pulse is approximately equal to the time difference τ between the first input and the second input. The pulse output from the negative phase output terminal en of the differential EXOR circuit 5 is input to the differential amplifier 3. The differential amplifier 3 amplifies the difference between the reference voltage dp output from the reference voltage generation circuit 4 and the signal at the negative-phase output terminal en, and outputs the positive-phase outputs shown in FIGS. 5 (F) and 5 (G). The signal O2P and the inverted output signal O2N are output. The normal phase output signal O2P is time-integrated by a low-pass filter (not shown) and becomes an output signal of the FM demodulation circuit.

  As apparent from comparing the signal at the negative phase output terminal en of the differential EXOR circuit 5 shown in FIG. 5E with the signal at the negative phase output terminal cn shown in FIG. 2E, the same input FM signal is obtained. For the frequency f, the number of pulses per unit time is twice that of the first embodiment. Therefore, the FM demodulation circuit according to the present embodiment can double the conversion gain corresponding to the gradient when converting the frequency f of the FM signal into the voltage V as compared with the first embodiment. However, on the other hand, since the time interval between adjacent pulses of the positive phase output signal O2P and the inverted output signal O2N is approximately halved, if the frequency f of the input FM signal is increased, overlapping of the tails occurs between the adjacent pulses. , A problem arises that the linearity of the fV characteristic is rapidly deteriorated.

  Here, of the positive phase output and the negative phase output of the differential EXOR circuit 5, the signal output to the positive phase output terminal ep has a wider pulse width and a higher noise peak value. Therefore, in the present embodiment, the positive phase output terminal ep is not connected to the input terminal of the differential amplifier 3, and only the negative phase output terminal en of the differential EXOR circuit 5 is connected to the negative phase input terminal of the differential amplifier 3. To do. As a result, it is possible to select and output a negative phase output having a narrow pulse width and less noise out of the positive phase output and the negative phase output of the differential EXOR circuit 5, and avoid being affected by the signal of the positive phase output terminal ep. can do. Furthermore, in the present embodiment, the reference voltage dp is set lower than the intermediate potential of the output of the differential EXOR circuit 5, so that the pulse widths of the positive phase output signal O2P and the inverted output signal O2N are set shorter than the delay time τ. It becomes possible. With these two effects, in the present embodiment, in the differential EXOR circuit type FM demodulation circuit having a large conversion gain, low distortion fV characteristics can be achieved up to the high frequency region of the input FM signal. .

[Third Embodiment]
Next, a third embodiment of the present invention will be described. FIG. 6 is a block diagram showing the configuration of an FM demodulator circuit according to the third embodiment of the present invention. The same components as those in FIG. 1 are denoted by the same reference numerals. The FM demodulator according to the present embodiment is different from the first embodiment in that the load 6 is connected to the positive phase output terminal cp that is opened in the differential AND circuit 2 according to the first embodiment. It is. The load 6 is attached to the product of the output resistance of the negative phase output terminal cn of the differential AND circuit 2 and the capacitance attached to the output terminal cn, and to the output resistance of the positive phase output terminal cp of the differential AND circuit 2 and the output terminal cp. It is desirable to set the value so that the product with the capacity (load 6) becomes equal. The basic operation of the present embodiment is the same as the operation of the first embodiment described with reference to FIG.

  According to the present embodiment, the driving loads of the positive phase output terminal cp and the negative phase output terminal cn of the differential AND circuit 2 can be designed equally, the current balance of the differential AND circuit 2 is maintained, and the negative phase is maintained. It is possible to speed up the response of the signal output from the output terminal cn and reduce output noise. As a result, in this embodiment, it is possible to achieve fV characteristics with low distortion up to a region where the frequency f of the input FM signal is higher than in the first embodiment.

  In the present embodiment, the load 6 is connected to the positive phase output terminal cp of the differential AND circuit 2. However, in the second embodiment, the load 6 is connected to the positive phase output terminal ep of the differential EXOR circuit 5. You may make it do. Thereby, also in 2nd Embodiment, the effect similar to this Embodiment can be acquired.

  FIG. 9 shows an example in which a MOS transistor is used as a configuration example of the differential AND circuit 2. However, the present invention is not limited to this, and a different device such as a bipolar transistor or MESFET is used for the differential AND circuit 2. Even in this case, the present invention can be applied. It is within the scope of the idea of the present invention to configure the FM demodulator circuit by changing the number of stages of amplifiers at the front stage or the rear stage of the differential AND circuit or differential EXOR circuit.

  The present invention can be applied to an FM demodulation circuit.

It is a block diagram which shows the structure of the FM demodulation circuit used as the 1st Embodiment of this invention. It is an input-output waveform diagram which shows the signal of each part of the FM demodulation circuit which becomes the 1st Embodiment of this invention. It is a figure which shows the fV characteristic of the FM demodulation circuit used as the 1st Embodiment of this invention, and the conventional FM demodulation circuit. It is a block diagram which shows the structure of the FM demodulation circuit used as the 2nd Embodiment of this invention. It is an input-output waveform diagram which shows the signal of each part of the FM demodulation circuit which becomes the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the FM demodulation circuit used as the 3rd Embodiment of this invention. It is a block diagram which shows the structure of the conventional FM demodulation circuit. It is an input-output waveform diagram which shows the signal of each part of the conventional FM demodulation circuit. It is a circuit diagram which shows the structure of the differential AND circuit used for FM demodulation circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Differential delay circuit, 2 ... Differential AND circuit, 3 ... Differential amplifier, 4 ... Reference voltage generation circuit, 5 ... Differential EXOR circuit, 6 ... Load.

Claims (4)

Edge detection means for detecting an edge of a differential input FM signal and outputting the detection result in a differential format;
Differential amplification means in which only one of the positive phase input terminal and the negative phase input terminal is connected to the positive phase output terminal or the negative phase output terminal of the edge detection means;
A reference voltage generating circuit that applies a reference voltage to an input terminal that is not connected to the output terminal of the edge detection means, out of the positive phase input terminal and the negative phase input terminal of the differential amplification means, FM demodulator circuit. The FM demodulation circuit according to claim 1, wherein
The edge detection means includes
A differential delay circuit for outputting a differential signal obtained by delaying the differential input FM signal;
The differential input FM signal is used as a first input, the differential signal output from the differential delay circuit is used as a second input, and the logic of the first input and the second input is determined. An FM demodulation circuit comprising: a differential AND circuit that outputs a product result in a differential format. The FM demodulation circuit according to claim 1, wherein
The edge detection means includes
A differential delay circuit for outputting a differential signal obtained by delaying the differential input FM signal;
The differential input FM signal is a first input, the differential signal output from the differential delay circuit is a second input, and the first input and the second input are exclusive. An FM demodulating circuit comprising: a differential EXOR circuit that outputs a result of a logical OR in a differential format. The FM demodulation circuit according to claim 1, wherein
Furthermore, it has a load circuit connected to the output terminal which is not connected to the input terminal of the differential amplification means among the positive phase output terminal and the negative phase output terminal of the edge detection means. Demodulator circuit.

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