I am doing a DDS function generator by using ARDUINO microcontroller and AD 9850 chip module,the output waveform according to data sheet of DDS chip module is 1 V which is too low,therefore I need to design an amplifier for it which can generate output sinewave within 1-20 Vpp.And the problem I am facing right now is when frequency up to MHZ,the output from DDS chip module begin to decrease,when frequency is 38.5 MHz, the output amplitude equal to 250mV.
If you actually intend to use the DDS for something, especially to drive a load at radio frequencies, then it is absolutely essential for you to learn what “impedance” means. Start here: https://en.wikipedia.org/wiki/Electrical_impedance
It is impossible to properly specify an amplifier design for your generator without your answer to KeithB’s question.
Think of an audio amplifier: is the intended output a pair of earbuds, or a home theater speaker system?
this amplifier circuit will be connect to AD 9850 chip module,so the output will be a sinewave signal with amplitude 20 Vpp frequency range from 0.1 to 40 Mhz,so it can be use in any application like debugging,any application require sine waveform
In overly simple terms, the impedance is how much ‘omph’ the amp must supply. Again, if the amp driving a pair of ear buds, or thousands of speakers in an outdooe stadium? An amplifier that simply needs to drive a 1Meg impedance is very different that one that needs to drive a 4 ohm impedance. You specifications for the output do not include the type of circuit it must be driving. Read up on impedance and describe what your circuit must be driving.
Or, in other terms, you told us the voltage you need, but not how much current or power you need. If you are not sure, just say “50 ohms” which is a good general number for RF work. But it does mean you need more than a typical small-signal Op-Amp
ya,I am not sure how much impedance I am needed,as said by Keith, i think 50 ohms should be ok…and then I have found a circuit for the amplifier design as a reference as
for the variable gain amplifier as amplitude of the DDS is decreasing when f increasing ,but the problem is CLC5523 chip is obsolete,so any chip can replace it?
and then amplify with ths 6022( this is what I am planning to replace it with the TI6002 in the attachment) http://www.ti.com/product/ths6022
for the
,I am thinking why do need the level amplifier? can i straight connect it with the voltage divider into the input of Vg of variable gain amplifier?
The TI6002 is a differential line driver, intended for digital communication signals like HDMI.
I don’t think you’re going to find a 1 amp solution that provides 0dBW @ 40 MHz. You might need to split the DC - 40 MHz into 2 or more bands, each with it’s own gain and final power amps. What are you using this for ???
Mee_n_Mac:
The TI6002 is a differential line driver, intended for digital communication signals like HDMI.
I don’t think you’re going to find a 1 amp solution that provides 0dBW @ 40 MHz. You might need to split the DC - 40 MHz into 2 or more bands, each with it’s own gain and final power amps. What are you using this for ???
