TINA/Spice/OPA656: Simulating OPA656 Frequency response and Transient Response

Hi Arivalagan,

you need the equivalent circuit model of the microchannel plate and you need to know how the signal current is generated. Then you can run a TINA simulation.

Kai

Ok...but, what should I do to simulate the circuit with standard current source and measure the frequency response?

Hi Arivalagan,

you might want to have a look at this link:

A TINA-Ti bandwidth simulation of a TIA is shown here:

You can open the file given there and run it.

Kai

Hi Arivalagan

So Transimpedance is a an area I have worked on quite a lot which is why I did the companion part to the unity gain stable OPA656, the OPA657. High speed transimpedance design is described in detail (with bench test techniques) in the attached presesntation, the references to the original 1996 BurrBrown articles I wrote on this are also in here. Normally you can improve your performance by using decomp devices. I just recently reviewed applications and parts for decomp VFA here - 

If you had your source capacitance and what you are trying to do, it only take me about 5min to design and send a TINA sim file, 

If you had your source capacitance and what you are trying to do, it only take me about 5min to design and send a TINA sim file,

7762.Transimpedance design flow using high speed op amps.pptx

The faster MCP-PMTs (assuming this is what you are using) are a few picofarads in parallel with an almost infinite resistance.  You can contact Hamamatsu for advice on the circuit model, but for the very fast units, often the cabling and/or traces contribute more to the circuit model than the actual detector.  

The other thing to ask is if you even need an transimpedance amplifier.  The MCP detectors have so much gain that they can often directly drive a 50 ohm load.

Thank you so much, Mr.Michael Steffes. The presentation was of much help.

I don't know the exact input capacitance of the MCP plate array.

I'm adding a few more details of the requirement. 

The job given to me is: 

1) To design a TIA for Time-of-Flight Mass Spectrometer whose specification is to amplify a small current which comes out of a microchannel multiplier plate (MCP)array (MCP) whose gain is 10^6. I'm told that the maximum current that comes out of the MCP is between 1pA and 5pA at a maximum bandwidth of around 300 MHz. 

2) I should amplify the above current to a reasonable voltage so that it can be converted into a digital signal. I'm only concentrating now on the TIA part.

3)While doing so I need to do it with very good AC performance and transient performance (I've attached a few sample output waveforms) and more importantly the noise performance

Work was done so far:

I've designed a TIA with OPA656...I purchased an unpopulated PCB for OPA656 evaluation board and purchased the IC OPA656 along with other components and made my own BNC connectors (the diagram is shown in the attachment) and readied a TIA. Presently, I use 1Gohm feedback resistors but, I will sweep the values physically and will take measurements.

MCP capacitance: The system uses high voltage pulse and I'm only heard of the MCP plate capacitance to be few picofarads but, I'm not very sure about the value of the MCP plate capacitance. 

My plan and requirement:

Having said about my performance requirements, I've chosen to design TIA with OPA656, OPA657, OPA857, and OPA858, TIA with current feedback amplifiers and if necessary fully differential amplifiers and find the optimized solution for the problem at hand. I would like to build 4 to five amplifiers and take rigorous performance measurements. Before going to next opamp and design the amplifier, I would like to validate the design with Tina TI so that I can validate my design and compare the simulated results Vs the measured results. 

I prefer TI opamps over Linear Tech. ones after I got the much relevant support like the one I got from TI Precision Labs for Opamp and for Tina TI.

On seeing the response from you Mr.Michael Steffes such an experienced person I provided as much as details I can. If you could support me through my design it would be of great support to me.

Kindly support.

Regards

M Arivalagan

Research Scholar

Anna University

Chennai

India

Write-up.pdf

I am sorry Chennai, 

I have run a few test designs on the first stage, and with 300Mhz BW, there are no solution that do not show higher noise than your signal. Unless you can average, and I don't think you can, I don't see how you can pull 1pA signals out of a 300MHz noise power bandwidth. 

OK...

Can you please share me how to simulate the TIA, maybe let us consider the MCP plate capacitance to be few picofarads.

Also, how to simulate the AC, transient and noise performance of the TIA alone excluding the MCP multiplier plate.

Regards

M Arivalagan

Research Scholar

Anna University

Chennai

Hi,

The capacitance of the Micro Channel Plate is 28pF. Can you please show me how do I simulate the transimpedance amplifier with this input capacitance.

Regards

M Arivalagan

Research Scholar

Anna University

Chennai

India

Hi Chennai, 

You can simulate the transimpedance amplifier by using a "Current Generator" source in parallel with your capacitance that will be presented by the source to the input of the amplifier. From there you can just simulate like normal. 

Regards,