Oscilloscope with improved front-end circuit

Abstract

The invention relates to an oscilloscope with an improved front-end circuit. The oscilloscope includes the front-end circuit and a control processing module. The front-end circuit includes an input-stage buffer and addition circuit, a gain selectable amplifying module, an A / D conversion circuit and a D / A conversion circuit. The input-stage buffer and addition circuit is connected to the control processing module via the gain selectable amplifying module and the A / D conversion circuit sequentially. A gain selection output end of the control processing module is connected with an input end of the gain selectable amplifying module. The other end of the control processing module provides front-end-circuit offset signals via the D / A conversion module. The offset signals are output to the input-stage buffer and addition circuit. The oscilloscope improves a minimum resolution input by the ADC and reduces demands on the gain of a simulation front end and adopts switching of amplifiers of a plurality of gains in combination with digital gains so that cost is saved and a signal-to-noise ratio of input ADC signals is improved.

Description

technical field [0001] The invention relates to the field of electric variable testing, in particular to an oscilloscope with an improved front-end circuit. Background technique [0002] The input analog front-end circuit of an oscilloscope or other measuring instruments determines its key indicators such as noise, bandwidth, and dynamic range. The analog front-end circuit of the oscilloscope generally completes functions such as signal input attenuation, buffering, amplification, bias, and bandwidth limitation, and then sends it to the ADC for analog-to-digital conversion, and the converted data is displayed after processing. [0003] Vertical sensitivity is an important parameter of an oscilloscope. Vertical sensitivity indicates how well the vertical amplifier amplifies weak signals, usually expressed in millivolts per division. The typical value of the minimum volts that a digital oscilloscope can detect is about 1mV per vertical display scale. [0004] In the oscillo...

AI Technical Summary

Problems solved by technology

[0012] 1. High cost

[0013] In the prior art, the digitally controlled variable gain module is the key module for realization, and is generally composed of a digitally controlled variable gain amplifier, which can realize at least dozens of steps of gain changes, and the cost is generally high

[0014] 2. Loud noise

[0015] In the prior art, when the oscilloscope has the minimum vertical sensitivity, such as 2mV / div, it is necessary to set the digitally controlled variable gain module to a very large gain in order to amplify the small signal at 2mV / div to the input full-scale range of the ADC At this time, the noise of the variable gain module itself is also amplified by the gain multiple, resulting in the deterioration of the signal-to-noise ratio of the input ADC signal, which is finally reflected in the large noise of the oscilloscope when the vertical scale is small.

[0016] 3. Small dynamic range

[0017] When the vertical gear is small, the gain set by the variable gain module is relatively large. Since the output voltage range of the gain module is fixed and determined by the chip itself, when the gain is large, the amplitude of the input signal is very small, otherwise it can be The output of the variable gain module is saturated, and the amplifier is saturated, which may cause the amplifier circuit to work abnormally, or generate a DC bias to shift the waveform

It is finally reflected on the oscilloscope that when the gain of the variable gain module is at a higher gear, the dynamic range of the input signal is very small

[0018] 4. Vertical sensitivity calibration is complex

[0019] The accuracy of the vertical sensitivity of the oscilloscope needs to be calibrated, that is, the gain that needs to be set for each vertical sensitivity gear is calibrated through the input signal. In the prior art, the coarse adjustment module and the fine adjustment module need to be calibrated, and the calibration algorithm is complicated.

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