Broadband programmable gain amplifier with precise gain step size

Abstract

The invention belongs to the technical field of integrated circuits, in particular to a broadband programmable gain amplifier with precise gain step size. The broadband programmable gain amplifier comprises a passive attenuation network, an active gain controller and two fixed gain amplifiers. Firstly, a signal passes through the attenuation network, and the corresponding attenuation intensity isselected according to the size of an input signal to acquire a signal with moderate amplitude; the signal is amplified through a first-level fixed gain amplifier to enter the active gain controller to acquire a precise gain; and the signal is amplified through a second-level fixed gain amplifier to acquire a final signal. The active gain controller mainly consists of two connected feedback loops,and the precise gain step size is acquired through controlling the relative intensity of the two feedback loops. The invention can meet the requirements on continuous improvement of VGA gain precision and flat band width in systems, such as communication systems, disc reading systems and the like.

Description

technical field [0001] The invention belongs to the technical field of integrated circuits, and in particular relates to a high-precision variable gain amplifier. Background technique [0002] In the fields of wireless communication, disk reading, medical equipment, etc., the signal to be processed by the analog system has a large dynamic range. For example, a Code Division Multiple Access (CDMA) communication system requires a gain change of about 80dB. In order to obtain a signal with a relatively constant amplitude, an automatic gain control (AGC) loop is generally used in similar analog systems, which adjusts the gain of the link according to the amplitude of the received signal to keep the output amplitude constant. The core of the automatic gain control loop is a variable gain amplifier (VGA). The automatic gain control loop generates a control signal by comparing the output signal of the VGA with the reference signal, and controls the gain of the VGA to make the ampl...

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Problems solved by technology

In addition, the variable transconductance module 206 is in different biases when the MOS device is in the off state and the maximum transconductance state, and its characteristics are also very different.

Especially when it is close to turn-off, the MOS device is at the subthreshold, which does not satisfy the typical square rate relationship

Therefore, when the gain is close to the step size of the attenuator 202, a more serious error will occur

Moreover, only two variable transconductance modules 206 work in the variable transconductance array 203 at any moment, and repeated multiple variable transconductance modules 206 waste area and limit bandwidth

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