I'm designing a circuit to use an IF amplifier, specifically the ADL5536, to amplify the signal of an SiPM array consisting of the MicroFJ-60035 TSV SiPM by SensL. My goal is to use this amplifier to boost the output of a multiplexed array of SiPMs. However, this is my first time using an IF amplifier like this, so I was wondering why is the recommended layout different than a standard op-amp? Usually, with op-amps, you have a positive and negative voltage. However, according to the datasheet of the ADL5536, you only have a +5V power source that goes through a bias inductor, and there is no negative power source. Why is this layout necessary, and how is working with an IF amplifier different than a regular op-amp?

  • 3
    \$\begingroup\$ Look up transmission lines. Unless you are very familiar with these, you really want to stick to the manufacturers suggested layout from the datasheet. I am not going to write yet another "what are transmission lines" and "why is RF design not the same as analog design" \$\endgroup\$
    – Joren Vaes
    Jul 2, 2018 at 15:24
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    \$\begingroup\$ If you don't understand what @Joren said, then your only hope is to find a guy with a pointy hat and a wand. \$\endgroup\$ Jul 2, 2018 at 15:26
  • \$\begingroup\$ The datasheet doesn't have a PCB layout, so I think the question is about the circuit topology. In other words, why doesn't this amplifier have power supply pins like an ordinary op-amp? \$\endgroup\$
    – Phil Frost
    Jul 2, 2018 at 15:54
  • \$\begingroup\$ What frequency are you using with SiPM? What is the needed signal bandwidth? \$\endgroup\$
    – MadHatter
    Aug 7, 2021 at 19:44

2 Answers 2


Because it's not a standard op-amp.

It's basically an output device, with a bit of bias to keep it happy, which drives straight into the output line. There's no negative power supply as it's been designed to be used without.

For efficiency, the high current required is supplied through an external inductor. There's no way an inductor of the required size could be placed on chip.

With specified operation to 1GHz, and gain well beyond that, you'd better follow the data sheet recommendations exactly, unless you know exactly what you're doing.

  • \$\begingroup\$ The datasheet states that the IF amplifier's range is from 20 MHz to 1.0 GHz; so if I'm working with a signal outside of that frequency range, this is essentially worthless, correct? \$\endgroup\$ Jul 2, 2018 at 19:45
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    \$\begingroup\$ It's an IF amplifier, it won't work to specification below 20MHz. However, you may not need the specification it fails, which is probably distortion initially. Because this type of amp has a high bottom frequency, they may have designed the bias to stop working only a little below 20MHz as well, I would if I was designing it, means smaller, and so less expensive, on-chip capacitors. What is your specification? It never hurts to start with a specification. \$\endgroup\$
    – Neil_UK
    Jul 2, 2018 at 20:23

The circuit probably looks like this


simulate this circuit – Schematic created using CircuitLab

R3 may be 50 ohms, to provide some reverse termination, and boost the absorption of reflected energy.


This is not the circuit of an opamp.

  • \$\begingroup\$ You are not answering the question. -1 \$\endgroup\$
    – user94729
    Jul 3, 2018 at 6:26

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