DAC 7524 output gain 

Question

I am counting TTL pulses then converting the count using the ad7524. I need to amplify my output with a gain of +7.5, however the typical operating circuit diagram has an inverting op amp. Is it possible to have positive gain with one op amp or should I use two inverting amps in series (the first being connected as in figure 4 of the data sheet and the second simply having a gain of -1)? By the way I am using the ad745 since it has low noise amplification.

Again referencing figure 4 in the data sheet, what is the output gain given the values of R1 and R2?

Thanks for the feedback.

best,

ADIApproved · Accepted Answer

Hi, 
 Apologies for the delayed response. 
 Potentiometer R1 and resistor R2 are used for gain error compensation and not for the actual gain for the DAC. 
 Due to the architecture of the DAC, you would have a positive output using a single amplifier by having a negative reference voltage. Using two amplifiers with configuration similar to what you have suggested above will work as well. 
 You may want to check out the app note AN-320A and see Figure 1b which transposes the DAC configuration to provide gain. I have not tried this configuration but in theory it should work. Note that the multiplying capability of the DAC will be lost when you use this configuration. 
 If you only want to add gain to your circuit, you may want to take a look at app note AN-137 which discusses adding gain for a similar DAC configuration. 
 Regards, 
 Mark)