Signal reception circuit and isolated signal transmission device

1. A signal reception circuit comprising:

an input terminal;

an input reference terminal;

an output terminal;

an output reference terminal that has the same potential as the input reference terminal;

a normally-on type transistor that includes a first terminal directly connected to the output terminal, a second terminal directly connected to the output reference terminal, and a control terminal;

a first detector circuit, connected to the input terminal, the output terminal, and the output reference terminal, that detects an input signal applied between the input terminal and the input reference terminal, to apply an output signal between the output terminal and the output reference terminal, the input signal being a modulated signal that is generated by modulating a radio-frequency wave with a pulse signal; and

a second detector circuit, connected to the input terminal, the control terminal of the normally-on type transistor, and the output reference terminal, that detects the input signal applied between the input terminal and the input reference terminal, to apply a negative voltage pulse to the control terminal of the normally-on type transistor with the output reference terminal as a reference.

2. The signal reception circuit according to claim 1 , wherein the second detector circuit

applies, when the input signal takes a first amplitude, a first voltage value of 0 or a negative value to the control terminal of the normally-on type transistor with the output reference terminal as a reference, causing the normally-on type transistor to be in an on-state, and

applies, when the input signal takes a second amplitude greater than the first amplitude, a second voltage value smaller than the first voltage value to the control terminal of the normally-on type transistor with the output reference terminal as a reference, causing the normally-on type transistor to be in an off-state.

3. The signal reception circuit according to claim 1 , wherein the first detector circuit applies, as the output signal, a positive voltage pulse to the output terminal with the output reference terminal as a reference.

4. The signal reception circuit according to claim 1 , further comprising:

a diode connected between the control terminal and the output reference terminal.

5. The signal reception circuit according to claim 1 , further comprising:

a resistor connected between the control terminal and the output reference terminal.

6. An isolated signal transmission device comprising:

an oscillator that generates a radio-frequency wave;

a modulator that modulates the radio-frequency wave with a pulse signal to generate a modulated signal;

an electromagnetic resonance coupler that performs isolated transmission of the modulated signal by electromagnetic resonance; and

the signal reception circuit of claim 1 to which the modulated signal is input from the electromagnetic resonance coupler.

7. A signal reception circuit comprising:

an input terminal;

an input reference terminal;

an output terminal;

an output reference terminal that has the same potential as the input reference terminal;

a normally-on type transistor that includes a first terminal connected to the output terminal, a second terminal connected to the output reference terminal, and a control terminal;

a first detector circuit, connected to the input terminal, the output terminal, and the output reference terminal, that detects an input signal applied between the input terminal and the input reference terminal, to apply an output signal between the output terminal and the output reference terminal, the input signal being a modulated signal that is generated by modulating a radio-frequency wave with a pulse signal; and

a second detector circuit, connected to the input terminal, the control terminal of the normally-on type transistor, and the output reference terminal, that detects the input signal applied between the input terminal and the input reference terminal, to apply a negative voltage pulse to the control terminal of the normally-on type transistor with the output reference terminal as a reference,

wherein the first detector circuit includes:

a first coupling capacitor that includes a first terminal connected to the input terminal, and a second terminal,

a first diode that includes a cathode connected to the second terminal of the first coupling capacitor, and an anode connected to the output reference terminal,

a first inductor that includes a third terminal connected to the second terminal of the first coupling capacitor, and a fourth terminal, and

a first smoothing capacitor connected between the fourth terminal of the first inductor and the output reference terminal.

8. A signal reception circuit comprising:

an input terminal;

an input reference terminal;

an output terminal;

an output reference terminal that has the same potential as the input reference terminal;

a normally-on type transistor that includes a first terminal connected to the output terminal, a second terminal connected to the output reference terminal, and a control terminal;

a first detector circuit, connected to the input terminal, the output terminal, and the output reference terminal, that detects an input signal applied between the input terminal and the input reference terminal, to apply an output signal between the output terminal and the output reference terminal, the input signal being a modulated signal that is generated by modulating a radio-frequency wave with a pulse signal; and

a second detector circuit, connected to the input terminal, the control terminal of the normally-on type transistor, and the output reference terminal, that detects the input signal applied between the input terminal and the input reference terminal, to apply a negative voltage pulse to the control terminal of the normally-on type transistor with the output reference terminal as a reference,

wherein the second detector circuit includes:

a second coupling capacitor that includes a first terminal connected to the input terminal, and a second terminal,

a second diode that includes an anode connected to the second terminal of the second coupling capacitor, and a cathode connected to the output reference terminal,

a second inductor that includes a third terminal connected to the second terminal of the second coupling capacitor, and a fourth terminal, and

a second smoothing capacitor connected between the fourth terminal of the second inductor and the output reference terminal.

9. The signal reception circuit according to claim 7 , wherein the second detector circuit includes:

a second coupling capacitor that includes a first terminal connected to the input terminal, and a second terminal,

a second diode that includes an anode connected to the second terminal of the second coupling capacitor, and a cathode connected to the output reference terminal,

a second inductor that includes a third terminal connected to the second terminal of the second coupling capacitor, and a fourth terminal, and

a second smoothing capacitor connected between the fourth terminal of the second inductor and the output reference terminal.

10. The signal reception circuit according to claim 9 , wherein a threshold voltage of the first diode is higher than a threshold voltage of the second diode.

11. The signal reception circuit according to claim 9 , wherein an on-resistance of the first diode is lower than an on-resistance of the second diode.