Resonating device with single operational amplifier
A resonating device includes: an amplifying circuit having a first input terminal, and an output terminal for outputting an output signal; a first feedback circuit coupled between the first input terminal and the output terminal of the amplifying circuit; a second feedback circuit, coupled between the first input terminal and the output terminal of the amplifying circuit; and a gain adjusting circuit, having an input terminal for receiving an input signal, and a first output terminal coupled to the first input terminal of the amplifying circuit; wherein a first equivalent impedance on a first intermediate terminal in the first feedback circuit substantially equals a second equivalent impedance on a second intermediate terminal in the second feedback circuit, and the gain adjusting circuit is arranged to tune a transfer function from the input signal to the output signal.
1. A resonating device, comprising:
an amplifying circuit, having a first input terminal, and an output terminal for outputting an output signal;
a first feedback circuit, coupled between the first input terminal and the output terminal of the amplifying circuit, wherein the first feedback circuit comprise a T-network, and the T-network comprising:
a first resistor, having a first terminal coupled to the first input terminal of the amplifying circuit, and a second terminal coupled to the first intermediate terminal;
a second resistor, having a first terminal coupled to the first intermediate terminal, and a second terminal coupled to the output terminal of the amplifying circuit;
a third resistor, having a first terminal coupled to the first intermediate terminal, and a second terminal coupled to the reference voltage; and
a capacitor, having a first terminal coupled to the first intermediate terminal, and a second terminal coupled to a reference voltage;
a second feedback circuit, coupled between the first input terminal and the output terminal of the amplifying circuit, wherein the second feedback circuit comprise a T-network; and
a gain adjusting circuit, having an input terminal for receiving an input signal, and a first output terminal coupled to the first input terminal of the amplifying circuit;
wherein a first equivalent impedance on a first intermediate terminal in the first feedback circuit substantially equals a second equivalent impedance on a second intermediate terminal in the second feedback circuit, and the gain adjusting circuit is arranged to tune a transfer function from the input signal to the output signal.
2. The resonating device of claim 1 , wherein the gain adjusting circuit is arranged to tune a numerator of the transfer function.
3. The resonating device of claim 1 , wherein the amplifying circuit further comprises a second input terminal, and the second input terminal is coupled to a reference voltage.
4. The resonating device of claim 3 , wherein the amplifying circuit is a differential operational amplifier, the first input terminal is a negative input terminal of the differential operational amplifier, and the second input terminal is a positive input terminal of the differential operational amplifier.
5. The resonating device of claim 1 , wherein the first input terminal of the amplifying circuit is a virtual-ground terminal.
6. The resonating device of claim 1 , wherein the first output terminal of the gain adjusting circuit is directly coupled to the first input terminal of the amplifying circuit.
7. The resonating device of claim 1 , wherein the gain adjusting circuit comprises:
a first resistor, having a first terminal for receiving the input signal, and a second terminal coupled to the first input terminal of the amplifying circuit;
a first capacitor, having a first terminal for receiving the input signal, and a second terminal coupled to the first input terminal of the amplifying circuit;
a second resistor, having a first terminal for receiving the input signal; and
a second capacitor, having a first terminal coupled to a second terminal of the second resistor, and a second terminal coupled to the first input terminal of the amplifying circuit.
8. The resonating device of claim 7 , wherein the gain adjusting circuit further comprises:
a third resistor, having a first terminal coupled to the first terminal of the second capacitor, and a second terminal coupled to the first input terminal of the amplifying circuit.
9. The resonating device of claim 1 , wherein the gain adjusting circuit further comprises a second output terminal coupled to the first intermediate terminal of the first feedback circuit.
10. The resonating device of claim 9 , wherein the gain adjusting circuit further comprises:
a first resistor, having a first terminal for receiving the input signal, and a second terminal coupled to the first input terminal of the amplifying circuit;
a first capacitor, having a first terminal for receiving the input signal, and a second terminal coupled to the first input terminal of the amplifying circuit; and
a second capacitor, having a first terminal for receiving the input signal, and a second terminal coupled to the first intermediate terminal of the first feedback circuit.
11. The resonating device of claim 9 , wherein the gain adjusting circuit further comprises:
a first resistor, having a first terminal for receiving the input signal, and a second terminal coupled to the first input terminal of the amplifying circuit;
a first capacitor, having a first terminal for receiving the input signal, and a second terminal coupled to the first input terminal of the amplifying circuit; and
a second resistor, having a first terminal for receiving the input signal, and a second terminal coupled to the first intermediate terminal of the first feedback circuit.
12. The resonating device of claim 1 , wherein the gain adjusting circuit further comprises a second output terminal coupled to the second intermediate terminal of the second feedback circuit.
13. The resonating device of claim 12 , wherein the gain adjusting circuit further comprises:
a first resistor, having a first terminal for receiving the input signal, and a second terminal coupled to the first input terminal of the amplifying circuit;
a first capacitor, having a first terminal for receiving the input signal, and a second terminal coupled to the first input terminal of the amplifying circuit; and
a second capacitor, having a first terminal for receiving the input signal, and a second terminal coupled to the second intermediate terminal of the first feedback circuit.
14. The resonating device of claim 12 , wherein the gain adjusting circuit further comprises:
a first resistor, having a first terminal for receiving the input signal, and a second terminal coupled to the first input terminal of the amplifying circuit;
a first capacitor, having a first terminal for receiving the input signal, and a second terminal coupled to the first input terminal of the amplifying circuit; and
a second resistor, having a first terminal for receiving the input signal, and a second terminal coupled to the second intermediate terminal of the first feedback circuit.
15. The resonating device of claim 1 , wherein the gain adjusting circuit comprises:
a first resistor, having a first terminal for receiving the input signal, and a second terminal coupled to the first input terminal of the amplifying circuit;
a first capacitor, having a first terminal for receiving the input signal, and a second terminal coupled to the first input terminal of the amplifying circuit;
a second resistor, having a first terminal for receiving the input signal, and a second terminal coupled to the first intermediate terminal of the first feedback circuit;
a second capacitor, having a first terminal for receiving the input signal, and a second terminal coupled to the first intermediate terminal of the first feedback circuit;
a third resistor, having a first terminal for receiving the input signal, and a second terminal coupled to the second intermediate terminal of the second feedback circuit; and
a third capacitor, having a first terminal for receiving the input signal, and a second terminal coupled to the second intermediate terminal of the second feedback circuit.
16. A resonating device, comprising:
an amplifying circuit, having a first input terminal, and an output terminal for outputting an output signal;
a first feedback circuit, coupled between the first input terminal and the output terminal of the amplifying circuit, wherein the first feedback circuit comprise a T-network;
a second feedback circuit, coupled between the first input terminal and the output terminal of the amplifying circuit, wherein the second feedback circuit comprise a T-network, and the T-network comprising:
a first capacitor, having a first terminal coupled to the first input terminal of the amplifying circuit, and a second terminal coupled to the second intermediate terminal;
a second capacitor, having a first terminal coupled to the second intermediate terminal, and a second terminal coupled to the output terminal of the amplifying circuit; and
a third capacitor, having a first terminal coupled to the second intermediate terminal, and a second terminal coupled to the reference voltage; and
a resistor, having a first terminal coupled to the second intermediate terminal, and a second terminal coupled to a reference voltage; and
a gain adjusting circuit, having an input terminal for receiving an input signal, and a first output terminal coupled to the first input terminal of the amplifying circuit;
wherein a first equivalent impedance on a first intermediate terminal in the first feedback circuit substantially equals a second equivalent impedance on a second intermediate terminal in the second feedback circuit, and the gain adjusting circuit is arranged to tune a transfer function from the input signal to the output signal.