# Is this circuit connection is right in advance design system?

#### noor84

##### Member level 2
I want to make a simulation of Transimpedance amplifier circuit to measure the dB(TIA)and voltage gain using Advance Design System(ADS simulator).
Please, may you advise me if my circuit connection(in attachments) is right or not?

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#### BigBoss

-Term2 will load the circuit in regard of DC.Place a coupling capacitor.
-How DC Current Source (SRC4) will sink the current ?? Nonsense,..
-Your circuit is not Current Controlled, Voltage Controlled B-Class... It won't work..

#### noor84

##### Member level 2
-Term2 will load the circuit in regard of DC.Place a coupling capacitor.
-How DC Current Source (SRC4) will sink the current ?? Nonsense,..
-Your circuit is not Current Controlled, Voltage Controlled B-Class... It won't work..

Dear BigBoss,
I attached new pic with DC coupling capacitor.
Please, any solution for DC Current Source (SRC4) to sink current?

#### Attachments

• 159.6 KB Views: 7

#### BigBoss

Place an Ideal Inductor between supply line and Current Source so that the Current Source will able to sink its current.
But there are still configuration errors.. This circuit is not current controlled.
Photo Diode will drive a circuit by its current so when the light is dark, the current will be very low, when the light is bright, the current will flow into circuit.The configuration must be so to my knowledge.. Because Transimpedance means
$Z_{imp}=\frac {V_{out}} {I_{in}}$

So, the Input will be Current, the Output will be Voltage. But your Input ?? The Input Current cannot flow into MOSs' Gate..

#### noor84

##### Member level 2
Place an Ideal Inductor between supply line and Current Source so that the Current Source will able to sink its current.
But there are still configuration errors.. This circuit is not current controlled.
Photo Diode will drive a circuit by its current so when the light is dark, the current will be very low, when the light is bright, the current will flow into circuit.The configuration must be so to my knowledge.. Because Transimpedance means
$Z_{imp}=\frac {V_{out}} {I_{in}}$

So, the Input will be Current, the Output will be Voltage. But your Input ?? The Input Current cannot flow into MOSs' Gate..

Dear BigBoss,
From your knowledge, is my circuit cannot measure the value of transimpedance amplifier?
I made a change on the connection of the previous circuit and I attached it in the attachments(named my circuit).
This connection is taken from a connection can be found it in the wire-line App. in the design guide of ADS. the picture name( ADS circuit) in the attachments.
The results of the ADS circuit in the attachments.
So, can I depend on this circuit as I connected my circuit in the attachments(named my cct) to simulate and measure the Z(TIA) and gain.....etc?

#### Attachments

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• 149.8 KB Views: 6
• 134.4 KB Views: 3
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##### Full Member level 4
The basic circuit is a self biasing amp consisting of the N and P
MOSFETs, using R1 as source of DC and AC fdbk. It does function as
a TIA when current is passed thru R1, the output will be a V with

R1 nominally fairly high in value to produce adequate G for low currents
from photo diode.

https://www.analog.com/en/products/...ifiers/optical-transimpedance-amplifiers.html ap notes here as well

Note that relying on biasing from MOSFET Vth's is a poor solution as device to device variations
in Vth will cause the simple stage to bias up at significantly different bias points. Also bias
point very T sensitive due to Vth dependency on T. Also to get adequate G R1 wants to be large,
which is counter to speed, as always trade offs.....

Then nominally you want an AGC loop of some sort to manage the T & V dependencies of the
amplifier.

Regards, Dana.

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#### noor84

##### Member level 2
The basic circuit is a self biasing amp consisting of the N and P
MOSFETs, using R1 as source of DC and AC fdbk. It does function as
a TIA when current is passed thru R1, the output will be a V with

R1 nominally fairly high in value to produce adequate G for low currents
from photo diode.

https://www.analog.com/en/products/...ifiers/optical-transimpedance-amplifiers.html ap notes here as well

Note that relying on biasing from MOSFET Vth's is a poor solution as device to device variations
in Vth will cause the simple stage to bias up at significantly different bias points. Also bias
point very T sensitive due to Vth dependency on T. Also to get adequate G R1 wants to be large,
which is counter to speed, as always trade offs.....

Then nominally you want an AGC loop of some sort to manage the T & V dependencies of the
amplifier.

Regards, Dana.
Dear Dana,