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I'm a french student who work on a portable echograph for the "echopen" association : http://echopen.org/index.php?title=Main_Page I'm working on the analog part which is composed of theses parts: * Generate a high pulse voltage * Integrate a T/R Switch in order to protect the signal process circuit * Use an amplifier * Use a filter * Integrate an envelope detector * transmit the signal to a redpitaya

I would like to use an amplifier with a control on the gain (the third part). I searched the circuit about the AGC (Automatic Gain Control) but on internet and from some people I heard about a TGC that is used in the medical domain but I can't found any circuit and I don't find the difference. Could you help me please?

Thank you,

Farad

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    \$\begingroup\$ AGC is used when you have a signal but don't know its amplitude (e.g., radio receiver). TGC is specific to ultrasound. If you are creating an ultrasound image, I expect you may want to use both, but that the TGC would probably be done digitally. I've never worked with ultrasound before though; perhaps someone else on your project would know better. \$\endgroup\$
    – Justin
    Commented Jan 4, 2016 at 18:50
  • \$\begingroup\$ Thank you for your answer, Electronically and physically what's the difference? And about the function of the TGC? Why TGC is specific to ultrasound? Unfotunately, nobody in the project know better... \$\endgroup\$
    – uFarad
    Commented Jan 5, 2016 at 10:04

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Thankyou everybody,

I found some answers for those who are interresting by I post it. The TGC (Time Gain Compensation) is VGA (Variable Gain Amplifier) which is controlled by a ramp. This is especially for the ultrasound application because the amplitude of the signal is reduce through the time that's why a ramp as a signal on the VGA will increase the gain through the time. (If I'm right)

In order the case of the project where I'm working I will follow this figure: enter image description here

Farad

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Looks like there are pre-made TGCs as IC, some references being on the echopen website BOM. That being said, some interesting insights specific to TGCs mmcan be found on this paper: https://www.google.co.in/url?sa=t&source=web&rct=j&url=http://repository.tudelft.nl/assets/uuid:d14ba7c4-e387-4a07-afc8-17c28f292ab3/time-gain-compensation_amplifier_for_ultrasonic_echo_signal_processing.pdf&ved=0ahUKEwjwiquAtpXKAhXJHo4KHduaA1YQFggfMAE&usg=AFQjCNHqI3g3uvGz5rSurnaxtSTWktxtnw Hope that helps!

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  • \$\begingroup\$ Thank you very much, I'm working for echopen but I found my answers on a thesis from "Phillippe LEVESQUE" \$\endgroup\$
    – uFarad
    Commented Jan 6, 2016 at 16:39

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