Analysis of the Principle of Programmable Nuclear Spectrum Signal Amplifier

This circuit uses two parts: a first-stage 100-fold fixed amplification and a DAC programmable multiple amplification. The first-stage amplification uses operational amplifier positive feedback. The DAC programmable multiple amplification part controls the 12-bit high-speed DAC chip through a single-chip microcomputer, and uses the DAC's internal precision resistor network as the operational amplifier's feedback resistor to improve the amplification accuracy and achieve 1 to 1,000 times programmable amplification. Output voltage:

Wherein, the value range of D is 0 to 4 095.

The DAC programmable amplifier circuit is shown in Figure 5.

2.4 Baseline elimination

The baseline elimination circuit first inputs the shaped nuclear pulse signal into a first-order low-pass filter circuit to extract the DC component, and then subtracts it from the original signal to remove the DC component. The circuit implementation is shown in Figure 6.

3 Main performance indicators

After the programmable nuclear energy spectrum signal amplifier circuit designed in this paper has been made into a board, welded, and debugged, the power supply adopts a 7-20 V regulated power supply, and the circuit converts it to the required +5 V, -5 V. The signal input end passes through the pole-zero cancellation circuit. After debugging, the R and C values ​​are changed according to the frequency requirements of different inputs (X fluorescence and gamma rays) to achieve pole-zero cancellation. The subsequent first-stage amplification and shaping filtering of the nuclear signal are connected. The output signal is a quasi-Gaussian waveform with a flat top of the pulse. The DAC is controlled by a single-chip microcomputer. After testing, the programmable signal is amplified by 0 to 100 times, which fully realizes the design requirements. Figure 7 is the final test output waveform.

4 Conclusion

The programmable nuclear energy spectrum signal amplifier designed in this paper has been analyzed and designed, and the circuit board, welding and debugging have been proved by experiments to meet the design requirements of filtering and shaping the energy spectrum signal and 0-100 times programmable amplification. This design can be used in X-ray fluorescence and gamma spectrum measurement systems, achieving the versatility and flexibility of the design requirements. Compared with traditional nuclear signal amplification and shaping, the programmable signal amplifier designed in this paper also has the advantages of low power consumption and easy hardware miniaturization, meeting the design requirements of modern nuclear signal processing.