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How to design the encoder controllable gain amplifier?

by:HENGXIANG     2020-11-05
A and A/D/A + DSP is adopted to form the digital signal processing system, the scheme of the system of complex, high cost. Second, USES the programmable amplifier, because of using special chip, gain control is limited by the chip provided by ability, flexibility is poor, the cost is higher also. Three, it is well known that the gain of the amplifier is associated with resistance, change of corresponding resistance value can change the gain of the amplifier, because of the change in resistance is used to control the amplifier gain scheme has a clear concept, simple circuit composition, easy implementation, low cost, can better meet the practical requirements, usually adopts the scheme, the concrete implementation method has the following kinds: 1, through the small relay switch fixed resistance to change the resistance of different resistance, the fixed resistor is determined by way of theoretical calculation and after debugging. 2, using the resistance type optical coupler ( Such as AD521L/H) By controlling its luminous tube current resistance tolerance of the change. 3, adopting digital encoder ( Such as X9312, X9241, etc. ) Written to the encoder, through software control relevant register values to change the resistance tolerance. Adopt the method of small relays applies only to control the resistance of the less situation, when the total number of required control gain kinds is large, then formed the relay array, makes the circuit structure, the reliability of the control is greatly reduced. In addition, relay switching process will inevitably produce interference to other circuits. Resistance type optical coupler has good isolation effect, but with D/A conversion circuit and amplification circuit to work, its circuit is complex, the cost is higher. In addition, the resistance type optical coupler light emitting diode current and its resistance value is nonlinear relationship, it makes it harder to control. 3 kinds of methods adopting digital encoder, has the advantages of simple circuit structure, convenient use, as long as chooses digital encoder has a high enough resolution, can meet the requirements of the gain control. Can choose X9241M digital encoder, its internal, there are four encoder has three resistance, distinguish eed of 1/63, each encoder chip with I2C bus control, can choose different value to different voltage gain of the encoder, and by changing the encoder sliding side counter register values to change sliding at the fixed end resistance value, so as to realize the adjustment of gain.
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