Questions tagged [transconductance]
The transconductance of a device relates the current through the output of the device to the voltage across the input of the device.
62
questions
0
votes
3
answers
86
views
Converting 1 - 5V signal to 4 - 20mA signal
reference: https://www.analog.com/media/en/technical-documentation/technical-articles/D61_EN-Convert.pdf
I am trying to convert a 1-5V signal to a 4-20mA signal using this circuit but it was not ...
- 11
3
votes
2
answers
292
views
Interview Question
This Circuit was given.
I know every component of this circuit individually, I know feedback and gain margin and transconductance amplifier.
But the problem is how to start?
first, I was thinking to ...
- 180
0
votes
0
answers
31
views
How to derive effective transconductance versus oscillation amplitude in a oscillator?
In the page below in the lecture note shows a plot of effective transconductance versus oscillation amplitude.
How is it derived? Or is there any source to derive effective transconductance versus ...
- 1,623
2
votes
2
answers
82
views
Bidirectional voltage-to-current converter
How to make the following voltage-to-current converter bidirectional, so that bidirectional current can be driven through the load?
- 210
0
votes
2
answers
81
views
Push-Pull voltage-to-current converter
How to make the following voltage-to-current converter bidirectional, so that it maintains the requested current through the load, even when that load stores energy and attempts to oppose the ...
- 210
0
votes
1
answer
87
views
Calculation of transconductance in a MOSFET
I am teaching electronics. I have come across this formula for drain current in the syllabus that I am teaching. However, I have never seen it before. My question is where is this number -3 from ...
- 3
3
votes
1
answer
69
views
Interpreting the value of transconductance shown in a MOSFET datasheet. Why was that particular value chosen to be shown?
Context: I'm a beginner in electronics, self studying MOSFETS. I'm trying to understand why the manufacturer of this MOSFET decided to provide a single particular transconductance value in the ...
- 513
1
vote
0
answers
44
views
how to calculate rx, ro given gx and go from XSPICE
I have a set of XSPICE data extracted from multisim as can be seen in the attached image. How do I calculate the ro and rx (base spreading resistance) given the parameters go and gx.
Thanks
0
votes
1
answer
256
views
output resistance and transconductance in the calculation of NMOS common source voltage gain
For a NMOS, the transconductance gm is defined as id/vgs at a fixed VDS.
However when we calculate the small signal gain of a common source amplifier, we use vds = -id x RD and then vds = -gm x vgs x ...
- 21
0
votes
1
answer
77
views
Does transconductance of a NMOS in saturation vary if I double both 'W' and 'L'?
Gm for a mosfet in saturation is 2Id/Vov. Vov is constant and we expected the Id to be a constant too for both cases since Id(sat)=0.5*UnCox (W/L)(Vov^2), W/L is unchanged and there for Id should be a ...
- 649
-2
votes
3
answers
292
views
What makes transconductance negative?
Quote...
"transconductance is -1 amps/volt"
Refer to this link for the source of my question...
This reference lacks the negation of A/V while this reference includes it? I'm confused...to ...
- 1
1
vote
0
answers
75
views
Transconductance of MOSFET with channel-length modulation
As far as I understood, I think it could be derived as below.
$$
g_m = \frac{\sigma I_D}{\sigma V_{GS}} = \mu_n C_{ox} \frac{W}{L}(V_{GS}-V_{TH})(1+\lambda V_{DS})
$$
$$
= \sqrt{2\mu_n C_{ox}\frac{W}{...
- 41
0
votes
0
answers
71
views
Gmo2 from vout about differential amplificator
I'd like to know if this demostration is correct to calculate Gmo2 from vout about differential amplificator from this diagram :
1 : Gmo transconductance about Common Base configuration
2 : Gmo1 ...
- 99
2
votes
0
answers
90
views
LM13700 Gain Calculation
I pulled some LM13700 OTAs from an old board and tested them. All voltages, currents, and resistances were measured. I had the expected (approximate) voltage gain using the equation
\$ A=(R_2/(R_1+R_2 ...
- 21
0
votes
2
answers
320
views
How do you find the transconductance of an external crystal oscillator?
I am trying to connect an external crystal to my STM32F446RC MCU.
I am following this guide to check for the compatibility: https://www.st.com/resource/en/application_note/cd00221665-oscillator-design-...
- 39
2
votes
1
answer
658
views
Transconductance value in LTSpice
I am trying to work out how to specify the transconductance value or Kn for LTspice. I have a part I can't find a suitable model for so I'll need to create one. I've tried this before and got values ...
- 191
7
votes
1
answer
583
views
Can a floating capacitor terminal be used to collect electrons?
I want to collect charge from an electron beam source. For that, I'm proposing to put a floating capacitor with its bottom terminal floating and directly exposed to the electron beam gun. The top ...
0
votes
0
answers
138
views
MOSFET triode small-signal modeling
TL;DR: Why do seemingly all treatments of MOSFET small-signal operation ignore the nonzero \$g_m\$ contribution in triode? Is the implicit assumption here that if the MOSFET is operated in triode then ...
- 499
1
vote
2
answers
84
views
Modeling MOSFET Pole and Transconductance for use in Larger Overall Control System
Recently I began a project involving some active current limiting using a MOSFET and an Op Amp. It is part of a larger overall circuit involving other Amplifiers.
I would like to perform a block-...
- 149
0
votes
1
answer
619
views
Mosfet transconductance in the saturation region
what happens to the transconductance of a MOSFET in the saturation region if the gate-source voltage is less than the threshold voltage? Will the transconductance be negative since the equation is ...
- 13
0
votes
0
answers
39
views
Trans-conductance of the system
What will be the effective transconductance of the system? We have an amplifier of the voltage gain of -2 and R, C connected as shown. I believe We can't judge if the system is in negative feedback ...
0
votes
0
answers
45
views
Trans-conductance amplifier using CS MOS amplifier
What is the meaning of the text "Less control on input Impedance"?
Why did we add CS amplifier for this purpose?
0
votes
0
answers
68
views
Why is transconductance vs gate voltage graph for a mosfet not constant when drain current is a linear function of gate voltage?(in linear region)
Id=Kn(Vg-Vth)Vd in the linear region
This should imply that the transconductance is constant for constant Vd(drain voltage) but the graph is something else
0
votes
1
answer
147
views
finding transconductance for common source amplifier
I wanted to check the transconductance formula I am using is correct when I am dealing with an amplifier that has a small signal (Vsig) and a DC signal(Vs). The schematic below is a little unclear but ...
0
votes
2
answers
171
views
JFET resistance and transconductance
The book says the rds of the 2N8461 JFET can be varied from 100 ohm to 10Meg.
I went on and tried to verify this using the equation and plug values in it from the datasheet
using the minimum values ...
- 75
0
votes
2
answers
546
views
MOSFET drain current equation vs on resistance
I have a very simple circuit. It’s just an n-channel enhancement MOSFET where Vgs is being driven to 9V and a relatively small 9ohm resistor sits between the 9V battery and drain terminal.
The way I ...
- 51
0
votes
1
answer
106
views
the transconductance of cascade MOSFET IF channel length modulation is NOT ZERO
What would the derivation of the cascode MOSFET transconductance in small signal analysis IF THE CHANNEL LENGTH MODULATION IS NOT ZERO, as most examples for the cascode mosfet transconductance say in ...
2
votes
2
answers
932
views
How does the Early effect limit the voltage gain?
As far as I understand, the Early effect increases the quiescent \$I_C\$ for a given \$V_{CE}\$.
At the same time texts treat this effect as a limiting factor for the gain.
Here is an excerpt from a ...
- 1,265
0
votes
0
answers
39
views
How to experimentally calculate transconductance of an OTA?
How can I experimentally calculate the transconductance of an Operational Transconductance Amplifier given that I know the value of bias current ?
1
vote
1
answer
255
views
Mathematical Model for SiC MOSFET C2M0080120D, transconductance and capacities [closed]
I am currently trying to use the model described in the paper "An Improved Analytical Model for Predicting the Switching Performance of SiC MOSFETs" in MathLab to simulate/imitate it. The paper can be ...
- 133
0
votes
1
answer
124
views
Plotting G(t) of an oscillator in Cadence
I have a cross-coupled NMOS-only oscillator that has its bias voltage changing so its transconductance is also changing over time. I want to plot its transconductance (G(t)=G0-gm/2) over time in ...
- 89
3
votes
1
answer
281
views
Constant-gm bias circuit
I am doing a study on Improvements in biasing and compensation of CMOS opamp.
Do you guys know how to come up with the equation for RDS4C ?
- 373
2
votes
1
answer
140
views
Error Amplifier Gain
I was studying the "SG3525" IC and its functions, and I encountered this issue:
In the "Error Amplifier" section of the Datasheet, there is a parameter that named "DC trans-conductance" which it is "...
2
votes
3
answers
209
views
Measuring transconductance of any circuit
May I know if the following transconductance measurement test circuit is correct because I am getting quite small Gm values ?
I suspect that I need to use some derivative function because changing ...
- 373
0
votes
1
answer
291
views
Advantages/Disadvantages of high/low transconductance efficiency (gm/Id) of NMOS/PMOS
From here, it's said that a higher gm/Id results in lower current consumption (which is usually preferred in low power operation) But what other effects does a high gm/Id have? Will it have other ...
user203020
4
votes
3
answers
5k
views
Understanding Operational Transconductance Amplifiers
I understand the high-level function of OTAs, that they provide an output current proportional to an input voltage. But what I don't understand, and what I can't seem to find any information on online,...
- 20.3k
0
votes
1
answer
161
views
OTA design, the Gm won't go down to zero
I'm trying to simulate a pseudo-differential OTA, but the the Gm vs Vin(differential) plot I obtain seems warped. The Gm won't go down to zero for large values of Vin.
attached is the circuit ...
- 3
0
votes
1
answer
228
views
Determine transconductance of a JFET given only voltage gain and internal drain resistance
I have a homework question as follows:
If a JFET having a specified value of rd=100 kΩ has an ideal voltage gain of Av(FET) = -200,
what is the value of gm ?
As far as I know, the closest formula for ...
- 107
1
vote
2
answers
7k
views
Common Source JFET Amplifier Gain
I would be thankful if someone could explain me what is the general formula used to calculate the gain of a common source jfet amplifier.
I have the fallowing circuit:
Since this circuit was taken ...
- 347
0
votes
1
answer
61
views
Transconductance of devices
I wanted to ask what are the cases when it's compulosory to know the transconductance (gm) of a device, whether it is BJT, JFET, MOSFET...
As far as I know, when you want fast switching with very ...
- 347
0
votes
1
answer
1k
views
Transconductance of a device
I would like to know what does it mean when someone says "that the transconductance of a FET or MOSFET is less compared to that of a bipolar junction transistor (BJT)".
I even heard someone saying ...
- 347
0
votes
1
answer
8k
views
Mosfet Voltage Gain in common-source configuration
I have some doubts about this so-called transconductance which can be either calculated for BJT or for FET transistors.
As far as I know, since BJTs are current controled devices, its transconductance ...
- 347
4
votes
1
answer
547
views
Subthreshold Transconductance Amplifier
As part of a broader project, I am designing IC circuit using CMOS to one of the first steps I'm working on is the filtering a series of pulses with of the noise. The actual pulses are around 1 kHz so ...
- 41
2
votes
1
answer
120
views
Is transconductance concept more important for FETs than in BJTs
In some texts I encounter they mention transconductance when it comes to FETs not BJTs. I have seen myself many texts and skimmed through them, the word transconductance does not appear until FETs. ...
- 3,430
1
vote
0
answers
247
views
what is normalized transconductance uesd for?
The transconductance is defined e.g. for BJT by
gm = dIc/dVBE with VCE=const (1)
where Ic is the collector current and VBE is base-emitter voltage, and from (...
- 11
4
votes
2
answers
2k
views
Why is higher transconductance relates to faster transistor switch?
Here is a quote from this site:
...higher 'transconductance' - a measure of the performance of a
transistor - than silicon transistors. The higher the
transconductance, the faster the ...
- 11.3k
2
votes
1
answer
20k
views
Transconductance of a MOSFET
I am trying to understand this formula to find the transconductance of a MOSFET transistor, but I am not getting the passage from the second to the third line. What happened there?
Thank you
1
vote
0
answers
207
views
Voltage to current converter using transconductance amplifiers, OPA860 and OPA861
I want to generate an ac current signal of 100 \$\mu\$A(peak to peak) with a bias current of 50 \$\mu\$A upto 100MHz frequency. This will be the input to a \$20 k \Omega\$ load.
I searched for some ...
user163517
1
vote
2
answers
77
views
Lack of data when performing hand calculations
This question refers to BJTs, FETs, MOSFETs, etc.
When I am designing a one or more staged BJT transistor circuit I am often considering differential base-emitter resistance aka "rπ" and finite ...
- 2,310
0
votes
2
answers
1k
views
Importance of Body Transconductance MOSFET
I am currently studying about small signal models of Common Drain & Common Gate configuration, where the body transconductance has significant effect on voltage gain and output resistance (when ...
- 2,310