Forums

Need help to design a transimpedance amplifier

Started by T Obulesu August 2, 2016
Hello  guys..

I want to design a trans-impedance amplifier to detect currents of the APD (in the range of 200 nA to 100 micro A).

Could some one suggest me the best IC with less bias current, single supply (+5 V only) and how to design a high sensitive TIA..? (typically, for every 100 nA change in the current, 100 mV voltage should be displayed).

On Mon, 1 Aug 2016 20:28:31 -0700 (PDT), T Obulesu
<obulesu.t@gmail.com> wrote:

>Hello guys.. > >I want to design a trans-impedance amplifier to detect currents of the APD (in the range of 200 nA to 100 micro A). > >Could some one suggest me the best IC with less bias current, single supply (+5 V only) and how to design a high sensitive TIA..? (typically, for every 100 nA change in the current, 100 mV voltage should be displayed).
Then 100 uA will make 100 volts. You'd have to range switch or something. Do you have access to Phil Hobbs' book? -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Tuesday, 2 August 2016 10:23:29 UTC+5:30, John Larkin  wrote:
> On Mon, 1 Aug 2016 20:28:31 -0700 (PDT), T Obulesu > <obulesu.t@gmail.com> wrote: > > >Hello guys.. > > > >I want to design a trans-impedance amplifier to detect currents of the APD (in the range of 200 nA to 100 micro A). > > > >Could some one suggest me the best IC with less bias current, single supply (+5 V only) and how to design a high sensitive TIA..? (typically, for every 100 nA change in the current, 100 mV voltage should be displayed). > > Then 100 uA will make 100 volts. > > You'd have to range switch or something. > > Do you have access to Phil Hobbs' book? > > > -- > > John Larkin Highland Technology, Inc > > lunatic fringe electronics
Hello H=Jhon Lerkin, Thanks for your swift response.. Well I don't have access to Phil Hobbs' book.. And whatever the maximum current I can detect upto 5V ...that is fine... But I am worrying about how to choose the suitable opamp and design parameters....
On 02/08/2016 04:28, T Obulesu wrote:
> Hello guys.. > > I want to design a trans-impedance amplifier to detect currents of the APD (in the range of 200 nA to 100 micro A). > > Could some one suggest me the best IC with less bias current, single supply (+5 V only) and how to design a high sensitive TIA..? (typically, for every 100 nA change in the current, 100 mV voltage should be displayed). >
Start simple with something like an LMP7701 and 1Meg feedback resistor. Get or borrow a copy of Horowitz and Hill "The Art of Electronics" the 3rd Edition. piglet
On Tuesday, August 2, 2016 at 4:44:00 AM UTC-4, piglet wrote:
> On 02/08/2016 04:28, T Obulesu wrote: > > Hello guys.. > > > > I want to design a trans-impedance amplifier to detect currents of the APD (in the range of 200 nA to 100 micro A). > > > > Could some one suggest me the best IC with less bias current, single supply (+5 V only) and how to design a high sensitive TIA..? (typically, for every 100 nA change in the current, 100 mV voltage should be displayed). > > > > Start simple with something like an LMP7701 and 1Meg feedback resistor. > > Get or borrow a copy of Horowitz and Hill "The Art of Electronics" the > 3rd Edition. > > piglet
+1 for AoE3.. chapter 8.11 does a nice job of talking about TIA's. (On a more basic level than Phil's book.) To the OP the next question is how much speed /BW you need? (and what's the input C of your APD?) George H.
On Tue, 2 Aug 2016 00:36:25 -0700 (PDT), T Obulesu
<obulesu.t@gmail.com> wrote:

>On Tuesday, 2 August 2016 10:23:29 UTC+5:30, John Larkin wrote: >> On Mon, 1 Aug 2016 20:28:31 -0700 (PDT), T Obulesu >> <obulesu.t@gmail.com> wrote: >> >> >Hello guys.. >> > >> >I want to design a trans-impedance amplifier to detect currents of the APD (in the range of 200 nA to 100 micro A). >> > >> >Could some one suggest me the best IC with less bias current, single supply (+5 V only) and how to design a high sensitive TIA..? (typically, for every 100 nA change in the current, 100 mV voltage should be displayed). >> >> Then 100 uA will make 100 volts. >> >> You'd have to range switch or something. >> >> Do you have access to Phil Hobbs' book? >> >> >> -- >> >> John Larkin Highland Technology, Inc >> >> lunatic fringe electronics > >Hello H=Jhon Lerkin,
???
>Thanks for your swift response.. >Well I don't have access to Phil Hobbs' book.. >And whatever the maximum current I can detect upto 5V ...that is fine... >But I am worrying about how to choose the suitable opamp and design parameters....
What sort of bandwidth/response time do you need? What is the photodiode bias voltage? What is the photodiode capacitance? Here's Phil's appnote on low-noise TIA's. There's more in his book. http://electrooptical.net/www/frontends/frontends.pdf -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Tuesday, 2 August 2016 08:58:42 UTC+5:30, T Obulesu  wrote:
> Hello guys.. > > I want to design a trans-impedance amplifier to detect currents of the APD (in the range of 200 nA to 100 micro A). > > Could some one suggest me the best IC with less bias current, single supply (+5 V only) and how to design a high sensitive TIA..? (typically, for every 100 nA change in the current, 100 mV voltage should be displayed).
Well....Bandwidth required is 1 MHz.. APD biasing voltage is 26-30V. Photodiode capacitance is 5pF
On 03/08/2016 04:43, T Obulesu wrote:
> On Tuesday, 2 August 2016 08:58:42 UTC+5:30, T Obulesu wrote: >> Hello guys.. >> >> I want to design a trans-impedance amplifier to detect currents of the APD (in the range of 200 nA to 100 micro A). >> >> Could some one suggest me the best IC with less bias current, single supply (+5 V only) and how to design a high sensitive TIA..? (typically, for every 100 nA change in the current, 100 mV voltage should be displayed). > > Well....Bandwidth required is 1 MHz.. > APD biasing voltage is 26-30V. > Photodiode capacitance is 5pF >
How about the OPA380 ? But my fastest opto TIA is only few kHz. piglet
On Wednesday, 3 August 2016 14:16:31 UTC+5:30, piglet  wrote:
> On 03/08/2016 04:43, T Obulesu wrote: > > On Tuesday, 2 August 2016 08:58:42 UTC+5:30, T Obulesu wrote: > >> Hello guys.. > >> > >> I want to design a trans-impedance amplifier to detect currents of the APD (in the range of 200 nA to 100 micro A). > >> > >> Could some one suggest me the best IC with less bias current, single supply (+5 V only) and how to design a high sensitive TIA..? (typically, for every 100 nA change in the current, 100 mV voltage should be displayed). > > > > Well....Bandwidth required is 1 MHz.. > > APD biasing voltage is 26-30V. > > Photodiode capacitance is 5pF > > > > How about the OPA380 ? But my fastest opto TIA is only few kHz. > > piglet
Yes...bandwidth is the constrain in this case...and bias current as well..
On Wednesday, August 3, 2016 at 4:46:31 AM UTC-4, piglet wrote:
> On 03/08/2016 04:43, T Obulesu wrote: > > On Tuesday, 2 August 2016 08:58:42 UTC+5:30, T Obulesu wrote: > >> Hello guys.. > >> > >> I want to design a trans-impedance amplifier to detect currents of the APD (in the range of 200 nA to 100 micro A). > >> > >> Could some one suggest me the best IC with less bias current, single supply (+5 V only) and how to design a high sensitive TIA..? (typically, for every 100 nA change in the current, 100 mV voltage should be displayed). > > > > Well....Bandwidth required is 1 MHz.. > > APD biasing voltage is 26-30V. > > Photodiode capacitance is 5pF > > > > How about the OPA380 ? But my fastest opto TIA is only few kHz. > > piglet
Huh, yeah something like that. To the OP, Putting in "rough" numbers. Say 1 Meg of feed back R, and another ~5pF of stray and opamp input C. So 1 Meg ohm*10 pF = 10^-5 sec, ~10^4 Hz (2*pi =~ 10) You'll need about a 100MHz GBW opamp. piglet's suggestion look good. George H.