What is Transfer function: Definition and 362 Discussions

In engineering, a transfer function (also known as system function or network function) of an electronic or control system component is a mathematical function which theoretically models the device's output for each possible input. In its simplest form, this function is a two-dimensional graph of an independent scalar input versus the dependent scalar output, called a transfer curve or characteristic curve. Transfer functions for components are used to design and analyze systems assembled from components, particularly using the block diagram technique, in electronics and control theory.
The dimensions and units of the transfer function model the output response of the device for a range of possible inputs. For example, the transfer function of a two-port electronic circuit like an amplifier might be a two-dimensional graph of the scalar voltage at the output as a function of the scalar voltage applied to the input; the transfer function of an electromechanical actuator might be the mechanical displacement of the movable arm as a function of electrical current applied to the device; the transfer function of a photodetector might be the output voltage as a function of the luminous intensity of incident light of a given wavelength.
The term "transfer function" is also used in the frequency domain analysis of systems using transform methods such as the Laplace transform; here it means the amplitude of the output as a function of the frequency of the input signal. For example, the transfer function of an electronic filter is the voltage amplitude at the output as a function of the frequency of a constant amplitude sine wave applied to the input. For optical imaging devices, the optical transfer function is the Fourier transform of the point spread function (hence a function of spatial frequency).

View More On Wikipedia.org
Recent contents Top users
  1. JasonHathaway

    Deriving transfer function of ramp response out of a plot

    Homework Statement The first order ramp unit response is shown in the graph below. Determine: 1. The transfer function. 2. Plot the error function e(t) then determine its maximum magnitude and the time http://s24.postimg.org/cdbhqm80j/Capture.png Homework Equations G(s)=(1/T)/(S+1/T) ... G(s)...
  2. I

    Second Order Approximation to Transfer Function

    Hi all, hopefully this is in the correct section here. Any help is really gratefully received. 1. Homework Statement I have a coursework, one question asks us to use a 2nd order approximation of the transfer function to..."estimate the settling time (5% of the settling value of output, peak...
  3. A

    Op amp transfer function determination ()

    Hey guys, need help with a problem here. Sorry for the quality of the image. I understand that above the op-amp, is the active low pass filter. So if I were to figure that out with respect to V2 and Vout, it would just be Vout/Vs = -(Zf/Zs) where Zf = (Rf/(1+jwCfRf)) Zs = Rs But I...
  4. Maxim Nol

    Unstable 4th order system (control theory)

    Homework Statement Hello everyone! To simplify, I have a system whose transfer function looks like this: G = (s^2-1) / (s^4-s^2-1) It's unstable and I have to find a way to stabilize it using PID controller and/or lead/lag compensators. Homework EquationsThe Attempt at a Solution So far I...
  5. S

    Calculate volume from first order transfer function

    Homework Statement In a gas pipeline a mixture of hydrogen in air is transported. Usually, the hydrogen content of the gas is 1 volume %. It is well below the lower explosive limit as a hydrogen / air mixture is 4 % by volume hydrogen. gas pipeline is positioned a detector that activates an...
  6. gfd43tg

    Transfer function algebraic manipulation

    Homework Statement Homework EquationsThe Attempt at a Solution I don't know if I am just stupid, but I can't see how to make this manipulation. I tried factoring the denominator $$ g_{p} = \frac {-1.43}{(s-1.399)(s+5.086)} $$ Then take out -1.399 and 5.086 $$ g_{p} = \frac...
  7. gfd43tg

    What are the Closed Loop Transfer Function Parameters for a PI Controller?

    Homework Statement Homework EquationsThe Attempt at a Solution I don't think you need to see the problem to figure this one out, if needed I will post it (takes up a lot of space in the thread). I know for a PI controller, the controller transfer function is given $$ g_{c} = k_{c} \frac...
  8. gfd43tg

    Sketching Transfer function in time domain

    Homework Statement $$ y(s) = \frac {s}{(s+1)(2s+1)} u(s) $$ Where ##u(s)## is the step function ##\frac {1}{s}## Find the output at t=0 and t= infinity Homework EquationsThe Attempt at a Solution My question is kind of basic, so I know the final and initial value theorem $$ \lim_{s \to 0}...
  9. gfd43tg

    Poles of transfer function and stability

    Homework Statement Homework EquationsThe Attempt at a Solution part a[/B] $$ \vec {x} = \left [ \begin{array}{ccc} X-X_{s} \\ S-S_{s} \end{array} \right ] $$ $$ \vec {u} = \left [ \begin{array}{ccc} S_{0}-S_{0s} \\ \frac {F_{0}}{V}- \big (\frac {F_{0}}{V} \big )_{s} \end{array} \right ] $$...
  10. perplexabot

    How to find transfer function of real world system?

    Hey all! I am trying to figure out how one goes about to try and find the transfer function (impulse response) of a real life system. Assuming the system is LTI. This "system" I speak of is a channel that is comprised of components such as linear amps, a mixer (can we even assume a mixer is...
  11. M

    This Fourier Transfer Function properties?.

    Hi Everyone. I want to know what do you think about this Transfer function: T(\omega) = \frac{e^{i\omega\tau}}{1-\rho e^{i2\omega\tau}} If\tau is Real, this function is "good and pretty"(?), because it has a "nice" representation in time with its inverse transform: a delay plus a series of...
  12. D

    Compute damping as a function of frequency

    Hi everyone, I'm french, so sorry for my bad english. I have a problem to compute the damping as a function of frequency. In fact, I plot the transfer function between the input (which is a force applied bu a hammer) and the output (which is an acceleration). Therefore, I can analyse the mode...
  13. Q

    Base excited stacked mass spring damper systems

    Homework Statement I'm trying to derive the equations of motion and state space as well as the transfer function for a system which has two mass spring damper systems stacked on top of each other. The system is base excited. I attached a pic of the system Homework Equations - Sum of the...
  14. H

    Why s is substitute with jw in transfer function?

    Can anybody explain to me briefly on why in a transfer function like G(s), we substitute s=jw such that it become G(jw) in order to find its gain value? Thanks
  15. S

    Inverse Discrete Laplace Transform

    Hi, I have an idea which when tested looks like its clearly flawed. I am hoping someone can tell me where my procedure is flawed, or point me to some other theory that has already done something similar. The first two are the laplace transform. The third line is the Fourier Transform. The...
  16. F

    Transfer function of cascaded filters

    1. Problem statement Find the transfer function , H(s) by two methods. Use Nodal analysis with Cramer's method, and decompose into simpler sections and use the property, H(s) = H1(s) * H2(s).Homework Equations H(s) = H1(s) * H2(s) H(s) = Vout/Vin Cramer's Rule. X = Dx/D : where D is the...
  17. can12345

    Correction Of Transfer Function

    Hello everyone; My question is regarding to velocity effect on transducer diaphragm. When fluid flow is acting to differential pressure transducer's diaphragm, the diaphragm is osculating(vibrating) and there will be fluid flow which is transverse(opposite flow,back flow) to normal fluid flow...
  18. S

    Transfer Function vs Frequency Response Function

    Ive read other threads on here about this and am still slightly confused about it. I did a little experiment; and I am hoping someone can help shed some light on the results. The experiment: 1. Create a system: modeled after a simple spring-mass-damper with mass=1 damping zeta=.1, natural...
  19. T

    Transfer function with Disturbance

    Homework Statement Find the steady-state error due to a disturbance Td(s) = 1/s. Set R(s) = 0. if given a system: Homework Equations n/a The Attempt at a Solution I need Y(s)/Td(s). To do this I must find Y(s) in terms of the transfer function Y(s)/R(s) which I have obtained. This gives me...
  20. T

    Calculating PhiG: Understanding the Phase Difference Between Waves at w=1

    Given w =1, What is phiG ? Is it the phase difference between the two waves? If it is, isn't it simply phiG = (delta t/T)*360 but I am not getting the right answer. PhiG = (0.5/2pi)*360 = 28.6 Also I don't know where this wt + phi = 2pi equation comes from.
  21. Stephengilbert1

    Engineering Finding the Transfer function of an RL series circuit

    Homework Statement Attached image has full question and information. Determine the transfer function of the circuit. I've done this part, what I am struggling with is converting it into the form requested. R = 10 KΩ L = 10 H Homework Equations Voltage divider: Vo = R2/(R1 + R2) Vin Impedance...
  22. A

    Solve RC Transfer Function with R=C=1

    Homework Statement R = C = 1; Homework Equations G(S) = 1/(s+1) The Attempt at a Solution Suppose R = C = 1 then the transfer function from the input voltage to the voltage across the capacitor is 1/ (s+1). So Vc(S) / V(S) = 1/(s+1). Getting back to time-domain: Vc(t) = V(t) * e^-t. What's...
  23. C

    Small-signal transfer function from this differential input

    Homework Statement 2. Homework Equations [/B] Small Signal Equivalent Circuit, Kirchhoff Current Law, and BJT equations mentioned in the question. The Attempt at a Solution It looks like I did something wrong. Can someone help me with fixing this?
  24. D

    Transfer function based question

    Homework Statement In order to increase number of poles in system we need to include A) zero at origin B) zero at infinity C) pole at origin D) pole at infinity Homework Equations [/B]The Attempt at a Solution Aren't the options linked ? I mean zero at infinity means a pole at origin and...
  25. E

    Transfer function - zero in a thermal heater

    Hi I am trying to characterize a microscale resistive heater. In my Bode plot there is decay that is less than -20dB/decade indicating that there is a zero in the system. Anyone having an idea of what physical meaning a zero in a resistive heater has? Thanks.
  26. I

    Engineering Designing a circuit from a transfer function

    Homework Statement Homework EquationsThe Attempt at a Solution So I know how to derive a transfer function from a given circuit, but not how to design a circuit from a transfer function like the one above. It seems like there's a huge amount of possible solutions and I don't know where to...
  27. T

    Transfer function for a system with lossless gears

    Homework Statement http://postimg.org/image/sd66qty27/ I am trying to understand the impedance terms for the equivalent system in (b) Homework Equations T1/T2 = N2/N1 The Attempt at a Solution I just don't understand why the impedance before the gears have to be multiplied by (N2/N1)^2...
  28. T

    Transfer Function of Block Diagram

    Homework Statement The block diagram of a PM DC servo motor with current loop feedback is shown below: If Ki is adjusted such that J(Ki+R)2 >> 4KTKbL, show that the transfer function may be approximated by G(s) = (1/Kb) / (τms+1)(τes+1), where τm = J(R+Ki) / KTKb τe = L / (R+Ki)The...
  29. STEMucator

    Can't see the error in the transfer function

    Homework Statement Here is the problem: Homework EquationsThe Attempt at a Solution Okay so I was REALLY confused as to why something wrong happened. Here is my work for the whole question: Sorry for the terrible writing. Okay so for part a), I derived the transfer function as...
  30. R

    Why the transfer function is represented in S Domain?

    Hi all, I would like to know why the Transfre function of the system is represented in S Domain instead of doing all the math in time domain itself. I studied a course on control systems and i wonder why s- domain is taken instead of other domains like Z- domain and others. Please refer belwo...
  31. I

    Internal combustion engine transfer function (request)

    Hello everyone, i need to find reported transfer functions of internal combustion engines for a project, i would appreciate the model of a four cylinder engine. If anyone knows about a book or some article which i can use, please let me know. thank you very much. the topic is related with...
  32. Captain1024

    Help Finding Transfer Function Vo/Vs

    Homework Statement Find ##a)\ H(s)=\frac{V_o}{V_s}## of the filter in the circuit below. ##b)\ ##The center frequency ##\omega_0## ##c)\ ##The band-width B Correct answers: ##a)\ H(s)=\frac{6s}{12s^2+11s+1}## ##b)\ \omega_0=0.28\frac{rad}{s}## ##c)\ B=0.71\frac{rad}{s}##...
  33. Captain1024

    Help Finding the Transfer Function H(s)=Vi(s)/Ii(s)

    Homework Statement Find the transfer function ##H(s)=\frac{Vi(s)}{Ii(s)}## The circuit consists of a voltage source and a 5H Inductor in series with a 10Ohm Resistor which are in parallel with a 10uF Capacitor in series with a 500Ohm Resistor. ##\rightarrow## Diagram here. Homework Equations...
  34. S

    Transfer function and Bode plot

    Homework Statement Find the transfer function for the filter on the attached picture and sketch it in Bode diagram, if you know ##Q_0 =\frac{\omega _0L}{R}>>1## and ##\omega _0^2=\frac{1}{LC}##. Homework EquationsThe Attempt at a Solution If I am not mistaken, we defined the transfer...
  35. D

    Is there a problem with this Source Transformation?

    Hey guys, i did this source transformation as an alternate method to find the transfer function of a circuit, however I am getting a different transfer function of 2/(2s+(s+3)(s^2+1)) to the solution in the following image. Any help would be really appreciated :)
  36. Z

    Transfer function of the state space model

    I have a state space model along with an observer and state feedback. I need to find the transfer function connecting the r (reference) to the y (output) I have this model on simulink. I know the A,B,C,D matrices. So, I can get the TF for the stateSpace with ss2tf function of matlab...
  37. N

    Transfer Function of Potentiometer

    Hey guys, I am new to this forum. I am working on a problem analyzing a potentiometer accelerometer. For the first part, I need to find the transfer function of the potentiometer. known: y=x2-x1 dynamic system: y,x1 For the mechanical aspect of the problem, I found that the transfer function...
  38. Rectifier

    Transfer function to phase transfere

    Hello! This is problem is a part of a bigger problem which I solved and came to a formula which is correct. This is the equation for one transfer function. The next thing I would like to find out here is when arg(H(jw)) is -90 or 90 degrees but I get stuck. Transfer function: ## H(jw) =...
  39. J

    Get transfer function from block diagram

    Hello guys! 1 & 2: I would like to get some help to take everything in A and find transfer function at B and C. I can't find these answer... 3. I know how to go from b) to c) .. we only multiply by E(s) and B(s). But I can't find b) at first. Thanks so much! JPGraphX
  40. U

    Optical Transfer Function of a microscope

    Hi all, I am wondering in the 3D optical transfer function as shown below: http://www.purplebark.net/mra/research/votf/otf-sliced-volume.png The m and n axes represent support of lateral spatial frequencies and the s axes axial. If we were talking about a microscope then it has what's called...
  41. E

    How to get valid frequency for a transfer function?

    Homework Statement transfer function: H(s) = 1/(s^2+s+1). question: compute half-power frequency Homework Equations none The Attempt at a Solution [/B]I got 4 answers: -0.605i, 0.065i, -1.169, 1.169 I know that only two of these are correct, one is 1.169 instead of -1.169 because frequency...
  42. A

    Is transfer Function of a mathematical system unique?

    I have gone through a mathematical modelling of a mass spring dashpot system in which if substitute differently we get different transfer functions. How does this really happen as we say Transfer function of a system is unique.
  43. W

    How can y be solved for given x and all A coefficients in the transfer function?

    If I have the following transfer function: x = A1 + A2*y + A3*sin(A4*y + A5) + A6*sin(A7*y + A8) +A9*sin(A10*y + A11) +A12*sin(A13*y + A14) I know x and all the A coefficients, how would one solve for y?
  44. C

    Transfer function between torque and strain

    I'm trying to develop a Matlab Simulink model which models the relationship between the voltage applied to a motor, and the voltage across a strain gauge connected to a shaft attached to the motor. So far, I have found the transfer function between voltage and motor torque, and the transfer...
  45. E

    Engineering Op-amp circuit analysis using a transfer function

    Homework Statement I have got transfer functions W(s) and Wk(s), where Wk(s) is correction transfer function. So I calculate W(s) and Wk(s) in series. Magnitude graph before correction: Magnitude graph after correction: The task is to make whole circuit and simulate it. Homework...
  46. gfd43tg

    Engineering Transfer function of Op-Amp circuit

    Hello, I am working on this previous final exam question. I am totally stumped with getting my answer with frequency. I believe my answer is correct with impedance, but I am having a hard time changing this to ω
  47. gfd43tg

    Transfer function of third order filter

    Hello, I am trying to do this example problem in my textbook I have my KVL and KCL equations written. I am trying to use substitutions to find V_c1 in terms of Vs and also in terms of Vout, so I can find Vout in terms of Vs. However, it seems like no matter what sequence of substitutions I do...
  48. A

    How to get transfer function (freq. domain) from Newton's 2nd Law Eqn

    Homework Statement I am given the following dynamic system. I want to find the transfer function, θ1(s)/T(s). The main body of the satellite, J1, acts like a large mass flying through space; space is essentially without friction and therefore no damping is imparted on the main body...
  49. gfd43tg

    Bode plot with given transfer function

    Homework Statement Homework Equations The Attempt at a Solution Hello, I am having serious problems being able to draw bode plots. At first the professor said to put everything into standard form with an (ω/ω_c)...and then there is also a table in the textbook with standard forms that don't...
  50. gfd43tg

    Engineering Transfer Function of a circuit

    Homework Statement For the circuit shown below: (a) Obtain an expression for H(ω) = Vo/Vi in standard form. (b) Generate spectral plots for the magnitude and phase of H(ω), given that R1 = 1 Ω, R2 = 2 Ω, C1 = 1 μF, and C2 = 2 μF. (c) Determine the cutoff frequency ωc and the slope of the...
Back
Top