Is there a solution to the slew rate when the Amplifier is current sensitive?

[Turbo95]

I am using ADA4817 Amplifier to make a current sensitive preamplifier. The current output from the detector is 2nA~ 60nA and the pulse width is only about 10ns. The problem of insufficient slew rate always appears during the simulation. May I have a solution?
I also read an article about ADA4817, and here is for reference.

ADA4817 Amplifier: Datasheet, Pinout and Applications

The ADA4817 amplifier is a kind of unity-gain stable, ultrahigh-speed, voltage feedback amplifier with FET inputs. This article enforces datasheet, pinout, applications, and other details about ADA4817.

www.utmel.com

 

[sdimen]

I am using ADA4817 Amplifier to make a current sensitive preamplifier. The current output from the detector is 2nA~ 60nA and the pulse width is only about 10ns. The problem of insufficient slew rate always appears during the simulation. May I have a solution?
I also read an article about ADA4817, and here is for reference.

ADA4817 Amplifier: Datasheet, Pinout and Applications

The ADA4817 amplifier is a kind of unity-gain stable, ultrahigh-speed, voltage feedback amplifier with FET inputs. This article enforces datasheet, pinout, applications, and other details about ADA4817.

www.utmel.com

Below are some suggestions to address the insufficient slew rate issue when using the ADA4817 for your current-sensitive preamplifier:

Review the Amplifier’s Specifications:
The ADA4817 has a typical slew rate of around 1500 V/µs. However, the effective slew rate in your application can be limited by the circuit’s loading, parasitic capacitances, and biasing conditions. Verify that your circuit meets the recommended conditions in the datasheet.

Minimize Parasitic Capacitance:
With a very short pulse width (∼10 ns) and low input current, even small parasitic capacitances at the amplifier’s output or in the feedback network can degrade the slew rate. Ensure that your PCB layout is optimized to minimize trace capacitance and that the load on the amplifier is as light as possible.

Optimize the Gain-Bandwidth Trade-Off:
High gain settings can further reduce the effective slew rate. Check if you can adjust the gain or use a two-stage amplification scheme—first a low-noise current preamplifier followed by a voltage amplifier—so that each stage operates within a more favorable gain-bandwidth product.

Consider a Faster Amplifier:
If the application truly demands fast transient response beyond what the ADA4817 can offer (especially for a 10 ns pulse), you might need to evaluate alternative amplifiers with higher slew rates. Devices specifically designed for ultra-fast transient signals (for example, some of the LT or AD series with enhanced performance) may be more appropriate.

Simulation Accuracy:
Double-check your simulation settings. Make sure that the time step is sufficiently small to capture a 10 ns pulse accurately, and that the model for the ADA4817 reflects its high-speed performance characteristics.

By carefully addressing these points, you should be able to improve the transient response of your preamplifier. If you continue to encounter issues, consider sharing your detailed circuit schematic and simulation setup on forums or with the manufacturer’s technical support for further insights.

Hope this helps!