Band pass filter circuit and sensor device including the same
A band pass filter circuit includes an amplifier circuit having a first input terminal to receive a first analog signal; a second input terminal to receive a second analog signal; first and second output terminals; capacitors; and switches. In a first switching mode, the switches are controlled so that the amplifier circuit and a first group of the capacitors connected between the input and output terminals operate as a first band pass filter filtering the first and second analog signals in a differential mode. In a second switching mode, the switches are controlled so that the amplifier circuit and second and third groups of the capacitors form second band pass filters filtering each of the first and second analog signals in a single-ended mode.
1. A band pass filter circuit comprising:
an amplifier circuit having a first input terminal to receive a first analog signal, a second input terminal to receive a second analog signal, and first and second output terminals;
a plurality of capacitors; and
switches connected to the plurality of capacitors,
wherein,
the switches are controlled in a first switching mode to connect, among the plurality of capacitors, a first group of capacitors between the first and second input terminals and the first and second output terminals, to form in conjunction with the amplifier circuit a first band pass filter that filters the first and second analog signals in a differential mode, and
the switches are controlled in a second switching mode to connect, among the plurality of capacitors, a second group of capacitors between the first input terminal and the first output terminal and a third group of capacitors between the second input terminal and the second output terminal, such that the amplifier circuit, the second group of capacitors, and the third group of capacitors form second band pass filters to filter each of the first and second analog signals in a single-ended mode.
2. The band pass filter circuit of claim 1 , wherein the second band pass filters are configured to share one or more of the plurality of capacitors with the first band pass filter.
3. The band pass filter circuit of claim 1 , wherein at least one of the second group of capacitors and at least one of the third group of capacitors are included in the first group of capacitors.
4. The band pass filter circuit of claim 1 , wherein the amplifier circuit and the second group of capacitors are included in one of the second band pass filters to filter the first analog signal, and
the amplifier circuit and the third group of capacitors are included in another one of the second band pass filters to filter the second analog signal.
5. The band pass filter circuit of claim 1 , wherein during the first switching mode, the amplifier circuit includes the first input terminal as an inverting input terminal, the second input terminal as a non-inverting input terminal, the first output terminal as a non-inverting output terminal, and the second output terminal as an inverting output terminal.
6. The band pass filter circuit of claim 1 , wherein the plurality of capacitors includes:
a first gain capacitor connected between the first input terminal and the first output terminal; and
a second gain capacitor connected between the second input terminal and the second output terminal.
7. The band pass filter circuit of claim 1 , further comprising, among the plurality of capacitors:
first input capacitors connected in series to the first input terminal; and
second input capacitors connected in series to the second input terminal,
wherein the first analog signal is transmitted to the first input terminal through the first input capacitors, and
wherein the second analog signal is transmitted to the second input terminal through the second input capacitors.
8. The band pass filter circuit of claim 1 , wherein in the second band pass filters,
each of first and second capacitors among the second group of capacitors is configured to alternately perform integration on the first analog signal and output a first sampling signal, and
the first capacitor is connected to the second capacitor through a first connection node when performing the integration on the first analog signal, and is configured to perform integration of charges of the second capacitor together with the first analog signal and output the first sampling signal.
9. The band pass filter circuit of claim 8 , wherein in the second band pass filters,
the second capacitor is connected to the first capacitor through the first connection node when performing the integration on the first analog signal, and is configured to perform integration of charges of the first capacitor together with the first analog signal and output the first sampling signal.
10. The band pass filter circuit of claim 8 , wherein in the second band pass filters,
each of third and fourth capacitors among the third group of capacitors is configured to alternately perform integration on the second analog signal and output a second sampling signal, and
the third capacitor is connected to the fourth capacitor through a second connection node when performing the integration on the second analog signal, and is configured to perform integration of charges of the fourth capacitor together with the second analog signal and output the second sampling signal.
11. The band pass filter circuit of claim 10 , wherein in the second band pass filters,
the fourth capacitor is connected to the third capacitor through the second connection node when performing the integration on the second analog signal, and is configured to perform integration of charges of the third capacitor together with the second analog signal and output the second sampling signal.
12. The band pass filter circuit of claim 1 , wherein in the first band pass filter,
a first capacitor among the first group of capacitors is configured to perform integration on the first analog signal and output a first sampling signal through the first output terminal, and
a second capacitor among the first group of capacitors is connected to the first capacitor through a first connection node and configured to store charges of the first capacitor.
13. The band pass filter circuit of claim 12 , wherein in the first band pass filter,
when the first capacitor performs the integration on the first analog signal, the second capacitor is connected to a third capacitor among the first group of capacitors through a second connection node, and
the third capacitor is configured to perform integration of charges of the second capacitor together with the second analog signal and output a second sampling signal through the second output terminal.
14. A sensor device comprising:
a sensor array; and
a sensor driver including a band pass filter circuit to filter first and second analog signals received from the sensor array,
wherein the band pass filter circuit includes:
an amplifier circuit having a first input terminal receiving the first analog signal, a second input terminal receiving the second analog signal, a first output terminal, and a second output terminal;
a plurality of capacitors; and
switches connected to the plurality of capacitors,
wherein,
the switches are controlled in a first switching mode to connect, among the plurality of capacitors, a first group of capacitors between the first and second input terminals and the first and second output terminals, to form, in conjunction with the amplifier circuit a first band pass filter that filters the first and second analog signals in a differential mode, and
the switches are controlled in a second switching mode to connect, among the plurality of capacitors, a second group of capacitors between the first input terminal and the first output terminal and a third group of capacitors between the second input terminal and the second output terminal, such that the amplifier circuit, the second group of capacitors, and the third group of capacitors form second band pass filters to filter each of the first and second analog signals in a single-ended mode.
15. The sensor device of claim 14 , wherein the sensor driver is configured to control the switches to operate the band pass filter circuit as the first band pass filter to sense a touch input of a body based on the first and second analog signals, and
the sensor driver is configured to control the switches to operate the band pass filter circuit as the second band pass filters to sense a touch input of a pen based on the first and second analog signals.
16. The sensor device of claim 14 , wherein the second band pass filters are configured to share one or more of the plurality of capacitors with the first band pass filter.
17. The sensor device of claim 14 , wherein at least one of the second group of capacitors and at least one of the third group of capacitors are included in the first group of capacitors.
18. The sensor device of claim 14 , wherein the amplifier circuit and the second group of capacitors are included in one of the second band pass filters and configured to filter the first analog signal, and
the amplifier circuit and the third group of capacitors are included in another one of the second band pass filters and configured to filter the second analog signal.
19. A switched capacitor integrator circuit for sampling analog input signals, comprising:
an operational amplifier having a first input terminal to receive a first analog signal, a second input terminal to receive a second analog signal, and first and second output terminals;
a plurality of capacitors; and
switches connected to the plurality of capacitors,
wherein,
the switches are controlled in a first switching mode to connect, among the plurality of capacitors, a first group of capacitors between the first and second input terminals and the first and second output terminals, to form in conjunction with the operational amplifier a first filter that filters the first and second analog signals in a differential mode, and
the switches are controlled in a second switching mode to connect, among the plurality of capacitors, a second group of capacitors between the first input terminal and the first output terminal and a third group of capacitors between the second input terminal and the second output terminal, such that the operational amplifier, the second group of capacitors, and the third group of capacitors form second filters to filter each of the first and second analog signals in a single-ended mode.
20. The switched capacitor integrator of claim 19 , wherein the first and second filters are each band pass filters.