CN102684623B - A kind of see-saw circuit based on the modulation of input branch switch - Google Patents

Abstract

The invention discloses a kind of see-saw circuit based on the modulation of input branch switch, primarily of resistance and operational amplifier composition, be connected in series a simulant electronic switch at the signal input part of circuit, described simulant electronic switch controls it by the control signal that a control end adds and opens or close.Circuit of the present invention can ensure that the multiplication factor of circuit is controlled continuously, overcomes the shortcoming that the multiplication factor of available circuit is intermittently controlled, and simplifies the design of multiple control circuit.

Description

A kind of see-saw circuit based on the modulation of input branch switch

Technical field

The present invention relates to a kind of circuit of electronic technology field, in particular, relate to a kind of see-saw circuit based on the modulation of input branch switch.

Background technology

In the design and devdlop of electronic circuit, amplifying the signal of telecommunication or decaying is one of modal treatment technology, wherein carries out the typical circuit of anti-phase amplification as shown in Figure 1 to voltage signal.The basis of Fig. 1 can form the see-saw circuit that multi-stage programmable as shown in Figure 2 controls.For simplicity, 4 grades of multiplication factors are merely illustrated in fig. 2.Control switch 1,2,3 or 4 can be distinguished by decoding circuit to connect, thus obtain 4 kinds of multiplication factors, be respectively-R ₂/ R ₁₁,-R ₂/ R ₁₂,-R ₂/ R ₁₃,-R ₂/ R ₁₄.

There is following shortcoming in the design of foregoing circuit: (1) this circuit includes decoding circuit, and circuit forms comparatively complicated, adds the production cost of circuit; If cancellation decoding circuit, then the control signal number of control switch break-make will increase, and the progression of multiplication factor is identical with switch controlling signal number.(2) progression of multiplication factor is limited, and along with the increase of multiplication factor progression, switch number should increase thereupon, and corresponding decoding circuit is more complicated.

Summary of the invention

The object of the invention is the technical problem for existing in above-mentioned prior art, a kind of see-saw circuit based on the modulation of input branch switch is proposed, this circuit can ensure that the multiplication factor of circuit is controlled continuously, overcome the shortcoming that the multiplication factor of available circuit is intermittently controlled, and simplify the design of multiple control circuit.

For achieving the above object, the technical solution adopted in the present invention is as follows:

A kind of see-saw circuit based on the modulation of input branch switch, primarily of resistance and operational amplifier composition, be connected in series a simulant electronic switch at the signal input part of circuit, described simulant electronic switch controls it by the control signal that a control end adds and opens or close.

Simulant electronic switch on described signal input branch road and the position of resistance can exchange.

The frequency of the control signal that described control end adds is n times of exaggerated signal frequency, n>100.

High-frequency filter capacitor in parallel on the feedback resistance of described operational amplifier.

The feedback resistance of described operational amplifier adopts T network form.

Compared with prior art, of the present invention brought beneficial effect is as follows:

(1) circuit of the present invention can ensure that the multiplication factor of circuit is controlled continuously, overcomes the shortcoming that the multiplication factor of available circuit is intermittently controlled;

(2) circuit of the present invention only uses an analog switch, simplifies the design of multiple control circuit.

Accompanying drawing explanation

Fig. 1 is the typical circuit figure of anti-phase amplification in prior art;

Fig. 2 is the see-saw circuit figure that in prior art, multi-stage programmable controls;

Fig. 3 is see-saw circuit figure mono-disclosed in this invention;

Fig. 4 is see-saw circuit figure bis-disclosed in this invention;

Fig. 5 is see-saw circuit figure tri-disclosed in this invention.

Embodiment

Below in conjunction with the drawings and specific embodiments, set forth the present invention further.These embodiments are interpreted as only being not used in for illustration of the present invention limiting the scope of the invention.After the content of having read the present invention's record, those skilled in the art can make various changes or modifications the present invention, and these equivalence changes and modification fall into the scope of the claims in the present invention equally.

The typical circuit figure at present voltage signal being carried out to anti-phase amplification shown in Fig. 1.The basis of Fig. 1 also can form the see-saw circuit that multi-stage programmable as shown in Figure 2 controls.For simplicity, 4 grades of multiplication factors are merely illustrated in fig. 2.Control switch 1,2,3 or 4 can be distinguished by decoding circuit to connect, thus obtain 4 kinds of multiplication factors, be respectively-R ₂/ R ₁₁,-R ₂/ R ₁₂,-R ₂/ R ₁₃,-R ₂/ R ₁₄.

Fig. 3 ~ Fig. 5 is the see-saw circuit figure based on the modulation of input branch switch disclosed in this invention, compared with Fig. 2 circuit, has been connected in series a simulant electronic switch S at signal input part.Switch S can be opened by controlling it at control end C access control signal or close.

Assuming that at C terminating logic high level, then switch S closes, and in C terminating logic low level, then switch S disconnects, otherwise also passable.

The operation principle of circuit of the present invention is as follows:

By inputting suitable pulse-width signal at control end C, the break-make of control simulation electronic switch S, changes input resistance R ₁equivalence value, thus change the amplification characteristic of circuit.As shown in Figure 3, hold the input cycle to be the control signal of T at C, the time that switch is closed is in one cycle T ₀, then in the average eguivalent value of cycle T internal feedback resistance

$R_{1\mathrm{eq}}=\frac{T}{T_0}{R}_1---\left(1\right)$

For making the equivalence value of input resistance in one-period as far as possible constant, the frequency of desirable switch controlling signal is n times of exaggerated signal frequency, according to result of the test, generally gets n>100.Such as, require that the frequency range of amplifying circuit is 0 ~ 100Hz, then the frequency of desirable switch controlling signal is greater than 100 × 100Hz=10kHz.

Electric capacity C in Fig. 3 ₂and C ₅for smooth signal waveform, suppress High-frequency Interference simultaneously.If the frequency range requiring signal to amplify is 0 ~ f _h, desirable C ₂≤ 1/ (2 π f _hr ₂), C ₅≤ 1/ (2 π f _hr ₅).Now circuit is at frequency 0 ~ f _hmultiplication factor in scope is

$A=\frac{u_o}{u_i}=\frac{R_2}{R_{1e}}\×\frac{R_5}{R_4}=\frac{R_2}{R_1}\×\frac{R_5}{R_4}\×\frac{T_0}{T}---\left(2\right)$

By control T ₀, or T, or duty ratio T ₀the size of/T, just can control the size of multiplication factor A.

Design example: by Fig. 3 circuit design one amplifying circuit, require that passband frequency range is 0 ~ 100Hz, multiplication factor is controlled continuously 1 ~ 10.

Design process: get R ₄=R ₅=10k Ω, R ₁=4.7k Ω, R ₂=47k Ω; Due to f _h=100Hz, desirable C ₂≤ 1/ (2 π f _hr ₂)=0.16 μ F, gets C here ₂=10nF; In like manner get C ₅=10nF; The frequency of switch controlling signal gets 100 × 100Hz=10kHz, then T=0.1ms.The multiplication factor of circuit is

$A=\frac{U_o}{U_i}=10\×\frac{T_0}{0.1\mathrm{ms}}=10D---\left(3\right)$

U in formula _i, U _obe respectively the amplitude of input, output signal; D=T ₀/ 0.1ms is duty ratio.From formula (3), when getting T ₀=0.1ms, when namely during D=100%, in Fig. 3, C end connects logic high all the time, the multiplication factor of circuit is 10; When getting T ₀=0.01ms, namely during D=10%, the multiplication factor of circuit is 1; Work as T ₀change within the scope of 0.01ms ~ 0.1ms, namely during D=10 ~ 100%, the multiplication factor of circuit changes between 1 ~ 10.

Table 1 gives above-mentioned design example and is 100Hz at frequency input signal, measured result when amplitude is 1V.

Table 1 measured result [u _i=sin (200 π t) V, the frequency of switch controlling signal gets 10kHz]

In the specific implementation, switch S and resistance R ₁position can exchange, as shown in Figure 4.Resistance R ₂and/or R ₅the form of T network can also be adopted, as shown in Figure 5.

For circuit shown in Fig. 5, multiplication factor is

$A=\frac{u_o}{u_i}=\frac{R_{21}+R_{22}}{R_{1e}}(1+\frac{R_{21}//R_{22}}{R_{23}})\×\frac{R_5}{R_4}=\frac{R_{21}+R_{22}}{R_1}(1+\frac{R_{21}//R_{22}}{R_{23}})\×\frac{R_5}{R_4}\×\frac{T_0}{T}$

In formula $R_{21}//R_{22}=\frac{R_{21}{R}_{22}}{R_{21}+R_{22}}.$

Claims (4)

1. the see-saw circuit based on the modulation of input branch switch, primarily of resistance and operational amplifier composition, it is characterized in that, a simulant electronic switch is connected in series at the signal input part of circuit, described simulant electronic switch is in series with a resistor, described simulant electronic switch controls it by the control signal that a control end adds and opens or close, described control signal is the periodic signal of variable duty ratio, by changing the size of described duty ratio, obtain the amplifying circuit multiplication factor set, the frequency of the control signal that described control end adds is n times of exaggerated signal frequency, n>100.

2. the see-saw circuit based on the modulation of input branch switch according to claim 1, it is characterized in that, the simulant electronic switch of described signal input part and the position of resistance can exchange.

3. the see-saw circuit based on the modulation of input branch switch according to claim 1, is characterized in that, high-frequency filter capacitor in parallel on the feedback resistance of described operational amplifier.

4. the see-saw circuit based on the modulation of input branch switch according to claim 3, is characterized in that, the feedback resistance of described operational amplifier adopts T network form.