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5V single power supply design and simulation of broadband amplifier

In Electronic Infomation Category: 5 | on April 19,2011

This design implements a 5 V single-supply the basic functions of a broadband amplifier. Core of high-speed op amp OPA820ID as an amplifier, THS3091D as the final stage amplifier, using DC-DC switch TPS61087DRC for the final stage power amplifier, 50 output load on the voltage gain of 40 dB. The amplifier pass band range of 10 Hz ~ 10 MHz, the system will eventually use the oscilloscope measuring the output voltage peak to peak and BC638 datasheet and RMS, and BC638 price and the MSP430 MCU 1602 using liquid crystal display output data. The whole system is simple, and BC638 suppliers and comprehensive application of the decoupling capacitor, filter and other measures to reduce the amplifier noise interference and suppress the self-excited. Proven, the program completed the design and some extensions.

1 demonstration program and system design

1.1 demonstration program

Directly using the integrated high-voltage output amplifier OPA820, the amplifier pass band from 20 Hz ~ 10 MHz, and can drive 50 load, the simple method used to complete the audio amplification power output. At the same time to do the load on the amplifiers maximum output without distortion output voltage 10 V peak to peak more difficult, so the use of DC-DC converter TPS61087DRC THS3091 amplifier circuit for the final stage power supply, the final design of this high-speed broadband amplifier. The program is simple, because a single chip, so the system smaller.

1.2 System Design

Using analog electronics and microprocessor signal acquisition and processing technology and the eventual gain control and output display. System block diagram shown in Figure 1.

Figure 1 System Block Diagram

2 Analog Circuit Design

Simulation using TIs software Tina, design, and 15 V 5 V power supply circuit and the third amplifier and peak detection circuit used by the microcontroller samples the output of LCD treatment. Tina simulation software to simulate the circuit when the passband 40 dB range 10 Hz ~ 10 MHz. Figure 2 shows the three amplifier pass band diagram.

Figure 2 three band-pass amplifier circuit diagram

2.1 amplifier

Use OPA820 as the first, second amplifier circuit, THS3091 amplifier circuit as the last stage. Three levels of magnification of 5 times, 5 times and 4 times. By the end of which two adjustable resistance level circuits to control the magnification and to ensure that the output signal is not distorted. Figure 3 shows the OPA820 and THS3091 chip design based on three-level amplifier.

OPA820 and THS3091 Figure 3 chip design based on three-level amplifier

2.2 Peak detection circuit

In the pass band range of low and high frequency two different inputs, so using two different detection circuit. Peak value detection circuit can refer to professional books on the specific circuit, high frequency peak detector circuit in the TPS61087 chip simulation using the circuit design shown in Figure 4.

Figure 4 high-frequency peak detector circuit

3 MSP430 MCU LCD output design

3.1 MSP430 MCU and LCD

MSP430 MCU is Texas Instruments (TI) 1996 began to market a 16-bit ultra-low power mixed-signal processors. Models using the MSP430F149 MCU, the use of A / D sampling signal peak detection circuit, programming in 1602 after the final completion of the LCD display output voltage peak and RMS data. In order to reduce power consumption, and reduce digital system to analog signal interference, the sampling is completed, the micro-controller design low-power mode. At the same time to real-time sampled data is not flashing, the programming time when using the timer interrupt after 1 s, so that only the LCD display once every 1 s sampling data. Circuit shown in Figure 5.

Figure 5 MCU and LCD circuit

3.2 Software Process

Software process, shown in Figure 6.

software flow chart of Figure 6

4 Performance Testing and Analysis

Test equipment are: TS1002 160 M Tektronix digital oscilloscope and RIGOL DS1022 20M source.

Test method is divided into three steps: (1) Connect +5 V, +15 V power supply, access to signal generator at the input signal. (2) Enter the pass band range of 10 Hz ~ 10 MHz, peak voltage signal 0 ~ 100 mV, test-pass band is flat. (3) change the frequency and RMS input voltage, output voltage were recorded peak and RMS.

Relevant test data shown in Table 1.

Table 1 40dB when the input and output test

Shown in Table 1, the amplifier in preset bandwidth 10 Hz ~ 10 MHz, maximum gain of 40 dB when the pass band is very flat. At this point the maximum undistorted output voltage of about 10.20 V. After testing, the biggest gain of the circuit is 42 dB. Out of production and commissioning physical map shown in Figure 7.

Figure 7 physical map

5 Conclusion

This design implements a 5 V single-supply the basic functions of a broadband amplifier to complete the systems hardware and software design, is more difficult to solve the distortion on the output load peak output voltage 10 V, output voltage peak detection, A / D sampling display and other issues.

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