I am currently working on amplifying the output sine wave of the TG5011 professional signal generator. Below are the specifications for the amplifier I am aiming to create:

  • Power Supply: A single supply of either 30V or 36V
  • Output Voltage: 30V peak-to-peak (30Vpp)
  • DC Offset: 15V DC
  • Bandwidth: 100kHz to 30MHz
  • Input Voltage: 1V peak-to-peak (1Vpp)

To achieve this, I am employing four cascaded op-amps, configuring two dual op-amp ICs in an inverting configuration with a 15V DC bias (please refer to the attached image). The required slew rate should be a minimum of 3000V/μs, as calculated by the formula SR = 2·π·Vout·f.

However, I have encountered a challenge in realizing this amplifier. Up until now, I have utilized the LM7372, which boasts a bandwidth of 120MHz. I am employing a gain of 3kOhm/1.3kOhm = 2.3 for each stage, theoretically resulting in a bandwidth of approximately 52 MHz. This worked flawlessly for each IC individually, but when connected together, the second IC overheated and ultimately burned out. Upon further investigation, I discovered that the LM7372 has limitations in its output swing voltage, which caused excessive heating and damage to the second IC.

I attempted to use the LM6172 (GBWP = 100 MHz); however, the gain dropped significantly at 15 MHz. I also experimented with the LM7171, but connecting the ICs together produced a substantial amount of harmonics and distortion.

I am now unsure of what I may be doing incorrectly and which op-amp model would be suitable for my application. I had contemplated using Current Feedback Amplifier (CFA) op-amps, but they are not recommended for inverting configurations and may introduce stability issues.

Do you have any recommendations for an op-amp model that I can employ to achieve my goal? I have attached an image of the schematic I am using for all the op-amps and the PCB design layout.

Note. I am not using the filter in the schematic.

I sincerely appreciate your assistance in advance.

enter image description here

enter image description here

enter image description here

  • 1
    \$\begingroup\$ Welcome to EE.SE. Interesting question, but you don't specify the load impedance which will be placed on the output, or the required input impedance. You also haven't stated the allowable distortion. Without these you amplifier isn't sufficiently specified to verify the integrity of the overall design. \$\endgroup\$
    – colintd
    Sep 26 at 11:53
  • \$\begingroup\$ Just some quick thoughts. Have you tried powering the OPAMPs using dual supplies (e.g. +/-15V)? I am aware of your design requirements, however, I have faced erratic behaviour when attempting to amplify AC signals with single supplies (Vcc/GND) even with "single supply" capable OPAMPs. Additionally, 15V BIAS sounds a bit too high for me, however, I need to carefully study the datasheets. \$\endgroup\$ Sep 26 at 12:01
  • 2
    \$\begingroup\$ You won't get 30 volts p-p from a 30 volt supply. \$\endgroup\$
    – Andy aka
    Sep 26 at 12:06
  • 1
    \$\begingroup\$ NB: the midpoint (R19-R22) is NOT "really" 15 V. You must use an "opamp follower" to make it true. \$\endgroup\$
    – Antonio51
    Sep 26 at 12:11
  • 1
    \$\begingroup\$ You should see something like this apexanalog.com/resources/products/pa107u.pdf \$\endgroup\$
    – Antonio51
    Sep 26 at 12:54


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.