Variable gain amplifier with dB linearity based on exponential function approximation
A technology of gain amplifier and exponential function, which is applied in the direction of gain control, amplification control, electrical components, etc., can solve the problem of loss of useful data of the preamble signal, and achieve the effect of simple structure
Active Publication Date: 2014-11-05
SOUTHEAST UNIV
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Therefore, on the one hand, the loop stabilization time of the automatic gain control loop must be shorter than the duration of the preamble, otherwise it will cause the loss of useful data after the preamble
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[0023] The present invention will be further described below in conjunction with the accompanying drawings.
[0024] Such as figure 1 Shown is a dB linear variable gain amplifier based on exponential function approximation. According to the idea of current complementarity, the variable gain amplifier builds a circuit structure based on an approximate exponential function (1+X) / (1-X); through The control signal S0, the control signal S1 and the control signal S2 control the work and disconnection of different branches of the input tube and the load tube, so as to obtain different equivalent input transconductance and equivalent load transconductance, and realize different gain control; by controlling The signal S3 converts the input transistor and the load transistor to expand the range of gain variation; the specific structure is as follows:
[0025] The first NMOS transistor M1, the third NMOS transistor M3, the fifth NMOS transistor M5, the seventh NMOS transistor M7 and ...
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The invention discloses a variable gain amplifier with dB linearity based on exponential function approximation, which adopts a thought of current complementation and employs on-off control to realize gain variation, implement approximation of a function (1+X) / (1-X) and obtain gain control within the linear range of an exponential function. A basic structure of the variable gain amplifier is an amplifier based on a transconductance structure, and gain thereof is a ratio of equivalent input transconductance to equivalent load transconductance. According to the variable gain amplifier, an approximate angle of the exponential function is constructed through a circuit, and different ratios of the equivalent input transconductance to the equivalent load transconductance are selected through on-off, so that the variable gain amplifier with the dB linearity is implemented. Owing to symmetry of a circuit structure, input and load can be interchanged, so that the gain variation range of the circuit is expanded. The variable gain amplifier has the advantages of simple structure and a more precise gain value.
Description
technical field [0001] The invention relates to a dB linear variable gain amplifier based on exponential function approximation, which is suitable for an automatic gain control circuit in a wireless transceiver and belongs to the wireless communication technology. Background technique [0002] Wireless sensor network is a new type of network composed of a large number of miniature sensor nodes, which has a wide range of applications. Due to the wide application of wireless sensor networks and the changing environment, the dynamic range of the signal strength received by the receiver is very large. If the gain of the receiving link is fixed, serious nonlinear distortion will easily occur when the input signal strength is high. If the amplifier is in a saturated state or a large signal is blocked, if the input signal is small, the useful signal will be easily overwhelmed by the noise, resulting in the failure of the subsequent circuit to demodulate. Therefore, it is necessary...
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IPC IPC(8): H03G3/20
Inventor 吴建辉姚红燕于天骥白春风黄成陈超田茜李红
Owner SOUTHEAST UNIV