Описание

More FPGA development modules:

High Speed 8 bit AD DA Module for FPGA Development Board 125MSPS DA Module 32M AD Module

Digital to analog converter (DA) circuit:

the DA circuit is composed of a high speed DA chip, 7-orderlow pass filter, amplitude

Regulating circuit and signal output interface.

High speed DA chip we are using AD's AD9708. AD9708 is a 8 bit, 125MSPS

DA conversion chip, built-in 1.2V reference voltage, a differential current output. The internal structure of the chipdiagram as shown below:

After the AD9708 chip differential output, in order to prevent noise interference, connected in the circuit of 7-order Bathurst low pass filter, the bandwidth is 40MHz, frequency response as shown below:

The filter parameters as shown below:

After the filters, we use 2 pieces of high performance 145MHz bandwidth operational amplifier AD8056, realize the difference Variational single ended, and amplitude adjustment and other functions, so that the whole circuitperformance has been improved to the greatest extent. Range regulation, is using the 5K potentiometer, the range of output end is -5V~5V (10Vpp).

Waveform display:

Analog-to-digital converter (AD) circuit:

the AD circuit is composed of a high speed AD chip, attenuation circuit and a signal input interface Form. High speed AD chip we are using 8 developed by AD company, the maximum sampling rate of 32MSPS .AD9280 chip. The internal structure as shown below:

According to the following configuration, we will set AD input voltage range to: 0V~2V:

Before the signal into the AD chip, we use a piece of AD8056 chip to construct the attenuation circuit, interface input range is -5V~+5V (10Vpp). Attenuation after, input range to meet the input range of the AD chip

(0~2V). The conversion formula is as follows:

When the input signal Vin=5 (V) , signal input to the Vad=2 AD (V);

When the input signal Vin=-5 (V), signal input to the Vad=0 AD (V);

1 * High speed AD/DA module

Experiment of the AD/DA module: