CN111464149B - Filtering amplifier - Google Patents
Filtering amplifier Download PDFInfo
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- CN111464149B CN111464149B CN201910047260.7A CN201910047260A CN111464149B CN 111464149 B CN111464149 B CN 111464149B CN 201910047260 A CN201910047260 A CN 201910047260A CN 111464149 B CN111464149 B CN 111464149B
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- 238000001914 filtration Methods 0.000 title description 9
- 239000003990 capacitor Substances 0.000 description 19
- 239000008186 active pharmaceutical agent Substances 0.000 description 5
- 229910044991 metal oxide Inorganic materials 0.000 description 4
- 150000004706 metal oxides Chemical class 0.000 description 4
- 239000004065 semiconductor Substances 0.000 description 4
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H11/00—Networks using active elements
- H03H11/02—Multiple-port networks
- H03H11/04—Frequency selective two-port networks
- H03H11/0416—Frequency selective two-port networks using positive impedance converters
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Abstract
The invention provides a filter amplifier, which comprises an amplifier circuit and a control circuit. The amplifier circuit includes a first amplifier and a first transistor. The first end of the first transistor is coupled to the first input end of the first amplifier. The control circuit includes a second amplifier, a second transistor, and a resistor. The first end of the second transistor is coupled to the first input end of the second amplifier. The control terminal of the second transistor is coupled to the output terminal of the second amplifier and the control terminal of the first transistor. One end of the resistor is coupled to the first input end of the second amplifier. Therefore, the filter amplifier can provide a wider filter frequency band and an accurate filter function.
Description
Technical Field
The present invention relates to an amplifier circuit, and more particularly, to a filter amplifier.
Background
In the conventional filter amplifier circuit architecture, the conventional resistor element collocated with the amplifier has a large area, and cannot achieve a very large or very small resistance value, so that the filter band of the filter amplifier is limited, and therefore, the specific operating characteristic of the transistor is usually utilized as a virtual resistor (pseudo-resistor) to be applied to the resistor element of the filter amplifier. However, the resistor value cannot be controlled accurately by using the transistor as the dummy resistor, so as to control the filtering frequency band of the filtering amplifier accurately. In view of this, how to expand the filtering frequency band of the filtering amplifier and effectively improve the accuracy of the filtering amplifier is a problem that is solved in the industry.
Disclosure of Invention
The invention provides a filter amplifier, which can expand the filter frequency band of the filter amplifier and can effectively improve the accuracy of the filter amplifier.
The filter amplifier of the present invention includes an amplifier circuit and a control circuit. The amplifier circuit includes a first amplifier and a first transistor. The first end of the first transistor is coupled to the first input end of the first amplifier. The control circuit includes a second amplifier, a second transistor, and a resistor. The first end of the first transistor is coupled to the first input end of the first amplifier. The first end of the second transistor is coupled to the first input end of the second amplifier. The control terminal of the second transistor is coupled to the output terminal of the second amplifier and the control terminal of the first transistor. One end of the resistor is coupled to the first input end of the second amplifier.
In an embodiment of the invention, all corresponding terminals of the first transistor and the second transistor are equipotential. The width-to-length ratio of the first transistor to the second transistor is N: m. The resistance value of the resistor is R. The equivalent resistance value of the first transistor is R.times.M/N.
In an embodiment of the invention, the first terminal of the first transistor and the first terminal of the second transistor are at the same potential. The second end of the first transistor and the second end of the second transistor are at the same potential.
In an embodiment of the invention, the second input terminal of the first amplifier and the second input terminal of the second amplifier are coupled to the same potential.
In an embodiment of the invention, the control circuit further includes a chopper and a comparator. The chopper is coupled to the first input terminal and the second input terminal of the second amplifier. The chopper is used for exchanging the voltage input paths of the first input end and the second input end of the second amplifier. The comparator is coupled to the chopper. The comparator is used for comparing the voltage of the output end of the first amplifier and the voltage of the other end of the resistor so as to generate a switching voltage to the chopper.
In an embodiment of the invention, a second terminal of the first transistor is coupled to the output terminal of the first amplifier. The second terminal of the second transistor is coupled to the output terminal of the first amplifier.
In an embodiment of the invention, the other end of the resistor is coupled to another output voltage corresponding to the output voltage provided by the output terminal of the first amplifier.
In an embodiment of the invention, the first input terminal of the first amplifier receives the input voltage via the second terminal of the first transistor.
In an embodiment of the invention, the other end of the resistor is coupled to another input voltage corresponding to the input voltage received by the first input terminal of the first amplifier via the second terminal of the first transistor.
In an embodiment of the invention, the amplifier circuit further includes a third transistor and a second control circuit. The first end of the third transistor is coupled to the second input end of the first amplifier. The second control circuit is coupled to the control terminal of the third transistor and provides a control voltage to determine an equivalent resistance value of the third transistor.
Based on the above, the filter amplifier of the present invention can use the transistor under the control architecture of the active virtual resistor (active virtual resistor) to be equivalent to the resistor in the circuit architecture of the filter amplifier, so as to provide a wider filter frequency band and an accurate filter function.
In order to make the above features and advantages of the present invention more comprehensible, embodiments accompanied with figures are described in detail below.
Drawings
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
FIG. 1 is a schematic circuit diagram of a filter amplifier according to an embodiment of the invention;
FIG. 2 is a circuit schematic of a control circuit according to an embodiment of the invention;
FIG. 3 is a circuit schematic of a filter amplifier according to another embodiment of the invention;
FIG. 4 is a circuit schematic of a control circuit according to another embodiment of the invention;
FIG. 5 is a circuit schematic of a differential filter amplifier circuit according to an embodiment of the invention;
FIG. 6 is a circuit schematic of a control circuit according to the embodiment of FIG. 5;
fig. 7 is a circuit schematic of an inverting amplifier circuit according to an embodiment of the invention.
Detailed Description
In order that the invention may be more readily understood, the following specific examples are provided as illustrations of the true practice of the invention. In addition, wherever possible, the same reference numbers will be used throughout the drawings and the description to refer to the same or like parts.
Fig. 1 is a circuit schematic of a filter amplifier according to an embodiment of the invention. Referring to fig. 1, the filter amplifier 100 includes an amplifier circuit 110 and a control circuit 120. The amplifier circuit 110 includes an amplifier 111, a transistor 112, and a capacitor 113. A first terminal of the transistor 112 is coupled to an input terminal of the amplifier 111, and a second terminal of the transistor 112 is coupled to an output terminal of the amplifier 111. A first terminal of the capacitor 113 is coupled to a first input terminal of the amplifier 111, and a second terminal of the capacitor 113 is coupled to an output terminal of the amplifier 111. A first input terminal of the amplifier 111 receives an input voltage V IN And the output of the amplifier 111 provides an output voltage V OUT . The control terminal of the transistor 112 receives the control voltage V G . In the present embodiment, the transistor 112 is used to implement an active virtual resistor (active virtual resistor) control architecture. When the three-terminal voltage of the transistor 112 is fixed by the control circuit 120, a virtual resistance (pseudo-resistor) of the transistor 112 can be adjusted by the resistor 123 to enable the amplifier circuit 110 to apply the input voltage V IN The filtering is performed stably.
The control circuit 120 includes an amplifier 121, a transistor 122, and a resistor 123. A first terminal of the transistor 122 is coupled to a first input terminal of the amplifier 121 to form a feedback path (e.g., negative feedback), and a second terminal of the transistor 122 is coupled to an output terminal of the amplifier 111. Transistor 112 is matched to transistor 122. The control terminal of the transistor 122 is coupled to the output terminal of the amplifier 121, and the output terminal of the amplifier 121 is coupled to the control terminal of the transistor 112 and the control terminal of the transistor 122. The output of the amplifier 121 provides a control voltage V G To the control terminal of transistor 112 and to the control terminal of transistor 122. In one embodiment, resistor 123 is an adjustable resistor (variable resistor). One end of the resistor 123 is coupled to the first input end of the amplifier 121, and the other end of the resistor 123 receives another output voltage V OUTN . A second input of the amplifier 121 is coupled to a second input of the amplifier 111. In the present embodiment, since the second terminal of the transistor 112 and the second terminal of the transistor 122 both receive the output voltage V provided by the output terminal of the amplifier 111 OUT The second terminal of transistor 112 is thus equipotential with the second terminal of transistor 122.
Transistors 112, 122 may be N-type transistors or P-type transistors, and the invention is not limited to the type of transistors 112, 122. In one embodiment, the transistors 112, 122 may be, for example, N-type metal oxide semiconductor (N-type Metal Oxide Semiconductor, NMOS) transistors or P-type metal oxide semiconductor (P-type Metal Oxide Semiconductor, PMOS) transistors.
In the present embodiment, the first input terminal of the amplifier 111 has a first voltage V A And a second input of the amplifier 111 has a second voltage V CM (common mode voltage). The first input of the amplifier 121 has a third voltage V B . Since the second input terminal of the amplifier 111 is coupled to the second input terminal of the amplifier 121, the second input terminal of the amplifier 111 and the second input terminal of the amplifier 121 are at the same potential, e.g. have the second voltage V CM . In this regard, the filter amplifier 100 of the present embodiment conforms to the following formulas (1) to (2), and the transistor 122 conforms to the following formulas (3) to (5) with the resistor 123.
V A ＝V CM ＝V B ………………………(1)
|V OUT -V CM |＝|V CM -V OUTN |………………………(2)
V R ＝V DS ………………………(3)
I R ＝I DS ………………………(4)
R＝R DS2 ………………………(5)
In the above formula (1), the first voltage V A Second voltage V CM Third voltage V B Are identical. In the above formula (2), the output voltage V OUT With a first voltage V A (equivalent to the second voltage V CM ) Subtraction is carried outThe absolute value of the result is equal to the first voltage V A With another output voltage V OUTN The absolute value after subtraction. In other words, another output voltage V of the embodiment OUTN Can be designed to output a voltage V OUT Related to the voltage relationship, e.g. V OUT <V CM <V OUTN Or V OUT >V CM >V OUTN And satisfies the above formula (2). In the above formula (3), the voltage V across the resistor 123 R Equal to the voltage across transistor 122V DS . In the above formula (4), the current value I through the resistor 123 R Equal to the current value I through transistor 122 DS . In the above formula (5), the resistance R of the resistor 123 is equal to the equivalent resistance R of the transistor 122 DS2 。
Based on the above formulas (1) - (5) and the circuit architecture of the filter amplifier 100, it can be further deduced that the transistor 112 and the transistor 122 have the same voltage V DS . Accordingly, as in the following equation (6), the aspect ratio (W 1 /L 1 ) Aspect ratio (W) with transistor 122 2 /L 2 ) Is N: m, and the equivalent resistance value R of the transistor 112 DS1 Equivalent resistance value R with transistor 122 DS2 The proportional relation of (2) is N: m. In other words, since the aspect ratio of the transistor 112 to the transistor 122 is N: m, the equivalent resistance of the transistor 112 is r×m/N. In the present embodiment, the equivalent resistance relationship among the resistance R of the resistor 123, the transistors 112 and 122 will satisfy the following formula (7).
Accordingly, the virtual resistance of the transistor 112 of the present embodiment is related to the resistance of the resistor 123 and the aspect ratio of the transistor 112 to the transistor 122. In other words, the user can design the resistance R of the resistor 123 and the aspect ratio of the transistor 112N and the aspect ratio M of transistor 122 to obtain any desired equivalent resistance value R of transistor 112 DS1 So that the transistor 112 can be designed to be equivalent to a maximum or minimum resistance value, and the equivalent resistance value R of the transistor 112 can be precisely controlled by controlling the three-terminal voltage of the transistor 122 DS1 Is effective in (1).
Fig. 2 is a circuit schematic of a control circuit according to an embodiment of the invention. Referring to fig. 2, the control circuit 220 of fig. 2 is an embodiment of another control circuit suitable for use in the filter amplifier 100 of fig. 1. In the present embodiment, the control circuit 220 includes an amplifier 221, a transistor 222, a resistor 223, a chopper (chopper) 224, and a comparator 225. Transistor 112 of fig. 1 is matched to transistor 222. A first terminal of the transistor 222 is coupled to the first input terminal of the amplifier 221, and a second terminal of the transistor 222 is coupled to the output voltage V of the amplifier circuit 110 shown in fig. 1 OUT . The control terminal of the transistor 222 is coupled to the output terminal of the amplifier 221, and the output terminal of the amplifier 221 is coupled to the control voltage V of the amplifier circuit 110 shown in FIG. 1 G And a control terminal of transistor 222. The output of the amplifier 221 provides a control voltage V G To the control terminal of transistor 222. One end of the resistor 223 is coupled to the first input end of the amplifier 221, and the other end of the resistor 223 receives another output voltage V OUTN . A second input terminal of the amplifier 221 is coupled to the second voltage V shown in FIG. 1 CM . The first and second inputs of the amplifier 221 are equipotential, e.g. have a third voltage V B 。
In the present embodiment, the chopper 224 is coupled to the first input terminal and the second input terminal of the amplifier 221. The chopper 224 is used for switching the voltage input paths of the first input terminal and the second input terminal of the amplifier 221. The comparator 225 is coupled to the chopper 224. The comparator 225 is used to compare the output voltage V of the amplifier circuit 110 shown in FIG. 1 OUT (i.e., the output of amplifier 111) and the voltage at the other end of resistor 223 to generate a switching voltage SEL to chopper 224. In the present embodiment, due to the input voltage V IN For time-varying voltage signals, e.g. sine wave signals, the output voltage V of the amplifier circuit 110 of FIG. 1 OUT May be higher or lower than the second voltage V CM . In this regard, the chopper 224 may be configured to switch the circuit paths of the first input terminal and the second input terminal of the amplifier 221.
Specifically, an input voltage V as received by the amplifier circuit 110 of FIG. 1 IN May be derived from, for example, an Electrocardiogram (ECG) signal, so that the comparator 225 may be based on an output voltage V output by the amplifier circuit 110 of FIG. 1 OUT To switch the first input and the second input of the amplifier 221 in real time to maintain the feedback path. In addition, after the control circuit 220 of the present embodiment is combined with the amplifier circuit 110 of fig. 1, the above formulas (1) to (7) are satisfied, so the detailed description of formulas (1) to (7) can refer to and analogize the teaching of the embodiment of fig. 1, and the detailed description thereof is omitted herein.
Fig. 3 is a circuit schematic of a filter amplifier according to another embodiment of the invention. Referring to fig. 3, the filter amplifier 300 includes an amplifier circuit 310 and a control circuit 320. The amplifier circuit 310 includes an amplifier 311, a transistor 312, and a capacitor 313. A first terminal of the transistor 312 is coupled to the input terminal of the amplifier 311, and a second terminal of the transistor 312 receives the input voltage V IN . A first terminal of the capacitor 313 is coupled to the first input terminal of the amplifier 311, and a second terminal of the capacitor 313 is coupled to the output terminal of the amplifier 311. A first terminal of the resistor 314 is coupled to a first input terminal of the amplifier 311, and a second terminal of the resistor 314 is coupled to an output terminal of the amplifier 311. A first input of the amplifier 311 receives an input voltage V via a transistor 312 IN And the output of the amplifier 311 provides an output voltage V OUT . The control terminal of the transistor 312 receives the control voltage V G . In this embodiment, the transistor 312 is used to implement an active virtual resistor control architecture. When the three-terminal voltage of the transistor 312 is fixed by the control circuit 120, the virtual resistance of the transistor 312 can be adjusted by the resistor 323 to enable the amplifier circuit 310 to output the voltage V IN The filtering is performed stably.
The control circuit 320 includes an amplifier 321, a transistor 322, and a resistor 323. A first terminal of the transistor 322 is coupled to a first input terminal of the amplifier 321 to form a feedback pathAnd a second terminal of transistor 322 is coupled to a first input terminal of amplifier 311. Transistor 312 is matched to transistor 322. The control terminal of the transistor 322 is coupled to the output terminal of the amplifier 321, and the output terminal of the amplifier 321 is coupled to the control terminal of the transistor 312 and the control terminal of the transistor 322. The output of the amplifier 321 provides a control voltage V G To the control terminal of transistor 312 and to the control terminal of transistor 322. In one embodiment, resistor 323 is an adjustable resistor. One end of the resistor 323 is coupled to the first input end of the amplifier 321, and the other end of the resistor 323 receives another input voltage V INN . Another input voltage V of the embodiment INN Can be designed to match the input voltage V IN Related to the voltage relationship, e.g. V IN <V CM <V INN Or V IN >V CM >V INN And satisfies the following formula (8). A second input of the amplifier 321 is coupled to a second input of the amplifier 311. In the present embodiment, since the second terminal of the transistor 312 and the second terminal of the transistor 322 both receive the output voltage V provided by the output terminal of the amplifier 311 OUT The second terminal of transistor 312 is thus equipotential with the second terminal of transistor 122.
|V IN -V CM |＝|V CM -V INN |………………………(8)
In the present embodiment, the first input terminal of the amplifier 311 has a first voltage VA, and the second input terminal of the amplifier 311 has a second voltage V CM (common mode voltage). The first input of the amplifier 321 has a third voltage V B . Since the second input terminal of the amplifier 311 is coupled to the second input terminal of the amplifier 321, the second input terminal of the amplifier 311 and the second input terminal of the amplifier 321 are at the same potential, e.g. have the second voltage V CM . In this regard, the filter amplifier 300 of the present embodiment can also analogize the results of the above formulas (1) - (7), so the relevant electrical characteristics of the filter amplifier 300 can be referred to the above description of the embodiment of fig. 1, and the description thereof will be omitted here. Accordingly, a user can obtain any desired transistor by designing the resistance value of the resistor 323, the aspect ratio of the transistor 312, and the aspect ratio of the transistor 322312, so that the transistor 312 is designed to be equivalent to a maximum or minimum resistance, and the three-terminal voltage of the transistor 322 is controlled to achieve precise control of the equivalent resistance R of the transistor 312 DS1 Is effective in (1).
Fig. 4 is a circuit schematic of a control circuit according to another embodiment of the invention. With reference to figure 4 of the drawings,
the control circuit 420 of fig. 4 is another embodiment of a control circuit suitable for use in the filter amplifier 300 of fig. 3. In the present embodiment, the control circuit 420 includes an amplifier 421, a transistor 422, a resistor 423, a chopper 424, and a comparator 425. Transistor 312 of fig. 3 is matched to transistor 422. A first terminal of the transistor 422 is coupled to the first input terminal of the amplifier 421, and a second terminal of the transistor 422 is coupled to the input voltage V of the amplifier circuit 310 of fig. 3 IN . The control terminal of the transistor 422 is coupled to the output terminal of the amplifier 421, and the output terminal of the amplifier 421 is coupled to the control voltage V of the amplifier circuit 310 shown in FIG. 3 G And a control terminal of transistor 422. The output of the amplifier 421 provides a control voltage V G To the control terminal of transistor 422. One end of the resistor 423 is coupled to the first input end of the amplifier 421, and the other end of the resistor 423 receives another input voltage V IN . The second input terminal of the amplifier 421 is coupled to the second voltage V of FIG. 3 CM . The first and second inputs of the amplifier 421 are equipotential, e.g. have a third voltage V B 。
In the present embodiment, the chopper 424 is coupled to the first input terminal and the second input terminal of the amplifier 421. Chopper 424 is used to switch the voltage input paths of the first input terminal and the second input terminal of amplifier 421. Comparator 425 is coupled to chopper 424. The comparator 425 is used for comparing the input voltage V of the amplifier circuit 310 shown in FIG. 3 IN (i.e., the input of amplifier 311) and the voltage at the other end of resistor 423 to generate a switching voltage SEL to chopper 424. In the present embodiment, due to the input voltage V IN For time-varying voltage signals, e.g. sine wave signals, the input voltage V of the amplifier circuit 310 of FIG. 3 is therefore IN May be higher or lower than the second voltage V CM . In this regard, the chopper 424 may be configured to switch the circuit paths of the first input terminal and the second input terminal of the amplifier 421.
Specifically, an input voltage V as received by the amplifier circuit 310 of FIG. 3 IN Can be derived from, for example, an electrocardiogram signal, so that the comparator 425 can be responsive to an output voltage V output by the amplifier circuit 310 of fig. 3 OUT To switch the first input and the second input of the amplifier 421 in real time to maintain the feedback path. In addition, after the control circuit 420 of the present embodiment is combined with the amplifier circuit 310 of fig. 3, the results of the above formulas (1) - (7) can be similarly analogized, so the relevant electrical characteristics can be referred to the description of the embodiment of fig. 1, and the description is omitted herein.
Fig. 5 is a circuit schematic of a differential filter amplifier circuit according to an embodiment of the invention. Fig. 6 is a circuit schematic of the control circuit according to the embodiment of fig. 5. Referring first to fig. 5, the differential filter amplifier circuit 510 includes a differential filter amplifier 511, transistors 512, 514, capacitors 513, 515, and input capacitors 516, 517. A first terminal of the transistor 512 is coupled to a first input terminal of the differential filter amplifier 511, and a second terminal of the transistor 512 is coupled to a first output terminal of the differential filter amplifier 511. The first output terminal of the differential filter amplifier 511 provides an output voltage V OUTP . One end of the capacitor 513 is coupled to the first input terminal of the differential filter amplifier 511, and the other end of the capacitor 513 is coupled to the first output terminal of the differential filter amplifier 511. A first terminal of the transistor 514 is coupled to the second input terminal of the differential filter amplifier 511, and a second terminal of the transistor 514 is coupled to the second output terminal of the differential filter amplifier 511. The second output terminal of the differential filter amplifier 511 provides an output voltage V OUTN . One end of the capacitor 515 is coupled to the second input terminal of the differential filter amplifier 511, and the other end of the capacitor 515 is coupled to the second output terminal of the differential filter amplifier 511. One end of the input capacitor 516 is coupled to the first input end of the differential filter amplifier 511, and the other end of the input capacitor 516 receives the first input voltage V IN . One end of the input capacitor 517 is coupled to the second input end of the differential filter amplifier 511, and the other end of the input capacitor 517 receives the second input voltage V IP . The control terminal of the transistor 512 receives the first control voltage V G1 And the control terminal of the transistor 514 receives the second control voltage V G2 。
Referring next to fig. 6, a control circuit 620 may be adapted for the differential filter amplifier circuit 510 of fig. 5. The control circuit 620 includes amplifiers 621, 624, transistors 622, 625, resistors 623, 626. Transistor 622 is matched to transistor 512 of fig. 5. A first terminal of the transistor 622 is coupled to a first input terminal of the amplifier 621 to form a feedback path, and a second terminal of the transistor 622 is coupled to a first output terminal of the amplifier 511 as in fig. 5. The control terminal of the transistor 622 is coupled to the output terminal of the amplifier 621, and the output terminal of the amplifier 621 is coupled to the control terminal of the transistor 512 and the control terminal of the transistor 622 as shown in fig. 5. The output of amplifier 621 provides a control voltage V G1 To the control terminal of transistor 512 and to the control terminal of transistor 622 as in fig. 5. In one embodiment, resistor 623 is an adjustable resistor. One end of the resistor 623 is coupled to the first input end of the amplifier 621, and the other end of the resistor 623 receives the output voltage V OUTP . A second input of the amplifier 621 receives a second voltage V CM 。
Transistor 625 is matched to transistor 514 of fig. 5. A first terminal of the transistor 625 is coupled to a first input terminal of the amplifier 624 to form a feedback path, and a second terminal of the transistor 625 is coupled to a second output terminal of the amplifier 511 as in fig. 5. The control terminal of the transistor 625 is coupled to the output terminal of the amplifier 624, and the output terminal of the amplifier 624 is coupled to the control terminal of the transistor 514 and the control terminal of the transistor 625 as in fig. 5. The output of the amplifier 624 provides a control voltage V G2 To the control terminal of transistor 514 and the control terminal of transistor 625 as in fig. 5. In one embodiment, resistor 626 is an adjustable resistor. One end of the resistor 626 is coupled to the first input of the amplifier 624, and the other end of the resistor 626 receives the output voltage V OUTN . A second input of the amplifier 624 receives a second voltage V CM . Accordingly, the filter amplifier composed of the amplifier circuit 510 of fig. 5 and the control circuit 620 of fig. 6 can be analogically applied to the above formulas (1) to (7), so the detailed description of formulas (1) to (7) can be referred to and analogically made to the teachings of the embodiment of fig. 1The illustration is not repeated here.
The virtual resistance of the transistor 512 of this embodiment is related to the resistance of the resistor 623 and the aspect ratio of the transistor 512 to the transistor 622. In other words, the user can obtain any desired equivalent resistance value of the transistor 512 by designing the resistance value of the resistor 623, the aspect ratio of the transistor 512 and the aspect ratio of the transistor 622, so that the transistor 512 can be designed to be equivalent to a maximum or minimum resistance value, or the equivalent resistance value of the transistor 512 can be precisely controlled. Similarly, the virtual resistance of the transistor 514 of the present embodiment is related to the resistance of the resistor 626 and the aspect ratio of the transistor 514 to the transistor 625. In other words, the user can obtain any desired equivalent resistance value of the transistor 514 by designing the resistance value of the resistor 626, the aspect ratio of the transistor 514 and the aspect ratio of the transistor 625, so that the transistor 514 can be equivalent to a very large resistance value after being designed, and the effect of precise control can be achieved by controlling the equivalent resistance value of the transistor 514.
Furthermore, the common-mode voltage and the first output terminal and the second output terminal of the differential filter amplifier circuit 510 can be voltages corresponding to each other. In other words, compared with the output voltage V received by the resistor 123 coupled to the first input end of the amplifier 121 of the control circuit 120 of the embodiment of FIG. 1 OUTN Can be designed to output a voltage V OUT In this embodiment, the resistor 623 coupled to the first input terminal of the amplifier 621 of the control circuit 620 can directly receive the output voltage V provided by the second output terminal of the transistor 511 OUTN And the resistor 626 coupled to the first input of the amplifier 624 of the control circuit 620 of the present embodiment can directly receive the output voltage V provided by the first output of the transistor 511 OUTP To generate a control voltage V G1 、V G2 . In the present embodiment, the output voltage V OUTN And output voltage V OUTP The voltage relationship of (a) is, for example, V OUTN <V CM <V OUTP Or V OUTN >V CM >V OUTP 。
FIG. 7 is an embodiment in accordance with the inventionIs a circuit schematic of an inverting amplifier circuit. Referring to fig. 7, the inverting amplifier circuit 710 includes an amplifier 711, transistors 712, 713, and a capacitor 714. In this embodiment, a first terminal of the transistor 712 is coupled to a first input terminal of the amplifier 711, and a second terminal of the transistor 712 is coupled to an output terminal of the amplifier 711. The control terminal of the transistor 712 receives the control voltage V G1 '. A first terminal of the transistor 713 is coupled to the first input terminal of the amplifier 711, and a second terminal of the transistor 713 receives the input voltage V IN . The control terminal of transistor 713 receives control voltage V G2 '. A first terminal of the capacitor 714 is coupled to a first input terminal of the amplifier 711, and a second terminal of the capacitor 714 is coupled to an output terminal of the amplifier 711. The second input of the amplifier 711 receives the second voltage V CM (common mode voltage) and the output of amplifier 711 provides an output voltage V OUT 。
The control manner and the circuit connection manner of the transistor 712 of the present embodiment can be matched to the circuit architectures of the control circuits 120 and 220 of the embodiments of fig. 1 and 2, and the control manner and the circuit connection manner of the transistor 713 of the present embodiment can be matched to the circuit architectures of the control circuits 320 and 420 of the embodiments of fig. 3 and 4. In other words, at least one of the feedback resistor (equivalent to the feedback resistor by the control transistor 712) and the input resistor (equivalent to the input resistor by the control transistor 713) of the inverting amplifier circuit 710 of the present embodiment can be applied to the control architecture of the active virtual resistor according to the above embodiments of the present invention, so as to achieve the effect that the transistors 712 and 713 can be designed to be equivalent to the maximum resistance value or the equivalent resistance values of the transistors 712 and 713 can be precisely controlled. In this regard, the coupling and implementation details of the circuit components of the amplifier circuit 710 may be analogized with reference to the descriptions of the embodiments of fig. 1 to 6, so that sufficient teachings, suggestions and implementation descriptions may be obtained, and thus are not repeated herein.
In summary, the filter amplifier of the present invention can be equivalent to at least one of the feedback resistor and the input resistor in the amplifier circuit by using the transistors, the equivalent resistance value of the controlled transistor is determined by adjusting the resistor in the control circuit and the width-to-length ratio of the other transistor, and the equivalent resistance value of the virtual resistor in the amplifier circuit is precisely controlled by controlling the three-terminal voltage of the other transistor in the control circuit. Therefore, the filter amplifier can obtain any required resistance value, and can provide accurate voltage signals so as to provide wider filter frequency bands and accurate filter functions.
Although the invention has been described with reference to the above embodiments, it should be understood that the invention is not limited thereto, but rather may be modified or altered somewhat by persons skilled in the art without departing from the spirit and scope of the invention.
Claims (9)
1. A filter amplifier, comprising:
an amplifier circuit comprising:
a first amplifier; and
A first transistor having a first end coupled to a first input of the first amplifier; and a control circuit including:
a second amplifier;
a second transistor, a first end of which is coupled to the first input end of the second amplifier, and a control end of which is coupled to the output end of the second amplifier and the control end of the first transistor;
a resistor, one end of which is coupled with the first input end of the second amplifier;
a chopper coupled to the first and second inputs of the second amplifier and configured to switch a voltage input path of the first and second inputs of the second amplifier; and
the comparator is coupled to the chopper and is used for comparing the voltage of the output end of the first amplifier and the voltage of the other end of the resistor so as to generate a switching voltage to the chopper.
2. The filter amplifier of claim 1, wherein all respective ends of the first transistor and the second transistor are equipotential, and wherein the aspect ratio of the first transistor and the second transistor is N: and M, wherein the resistance value of the resistor is R, and the equivalent resistance value of the first transistor is R.times.M/N.
3. The filter amplifier of claim 1, wherein the first terminal of the first transistor is at the same potential as the first terminal of the second transistor, and wherein the second terminal of the first transistor is at the same potential as the second terminal of the second transistor.
4. The filter amplifier of claim 1, wherein the second input of the first amplifier and the second input of the second amplifier are coupled to the same potential.
5. The filter amplifier of claim 1, wherein a second terminal of the first transistor is coupled to the output terminal of the first amplifier and the second terminal of the second transistor is coupled to the output terminal of the first amplifier.
6. The filter amplifier of claim 5, wherein the other end of the resistor is coupled to another output voltage corresponding to the output voltage provided by the output of the first amplifier.
7. The filter amplifier of claim 1, wherein the first input of the first amplifier receives an input voltage via a second terminal of the first transistor.
8. The filter amplifier of claim 7, wherein the other end of the resistor is coupled to another input voltage corresponding to the input voltage received by the first input terminal of the first amplifier via the second terminal of the first transistor.
9. The filter amplifier of claim 1, wherein the amplifier circuit further comprises:
a third transistor having a first terminal coupled to the second input terminal of the first amplifier; and
the second control circuit is coupled to the control end of the third transistor and provides a control voltage to determine the equivalent resistance value of the third transistor.
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