Metal-Oxide-Semiconductor ield Effect Transistor (MOSET) Source Gate Drain p p n- substrate - SUB MOSET is a symmetrical device in the most general case (for example, in an integrating circuit) In a separate MOSET device the source and substrate are jointed
Types of MOSET n-channel p-channel - - --------------------------------------------------------- Depleted n-channel Enhanced n-channel i DSAT i DSAT T < GS T > GS In Depleted MOSETs the drain current exists at GS
amily of MOSET Output characteristics n-channel i D f( SD ) GS const - SD - i D (ma).5 3 2.5 GS Linear region 5 5 DS () Saturation region
MOSET Transfer Characteristic n-channel i Dsat f( GS ) GS varies - i Dsat k ( GS - T ) 2 i Dsat (ma) 3 2 T g m i Dsat / GS -2 - GS () Transconductance g m is a function of GS
MOSET Transfer Characteristic i Dsat T -2 - GS () There is subthreshold drain current which decays exponentially below threshold voltage T
Ideal Operational Amplifier Any Op-Amp contains at least 5 terminals non-inverting input inverting input - CC (5) positive power supply OUT output EE (-5) negative power supply Ideal Op-Amp does the following Amplifies a differential signal ( - - ) and differential voltage gain A D is extremely high OUT A D ( - - ) A D Suppresses a common signal ( - ), i.e. OUT A C ( - ) A C
Properties of Ideal Op-Amp without eedback - OUT The input currents are negligible I, I -, Op-Amp has high input impeadances, - Low output impeadance OUT Transfer characteristic 5 OUT -2-2 Saturation -5 ( - - ), µ Linear egion
OpAmp with Negative eedback Negative feedback applies the output voltage to the input in the polarity to compensate the input voltage Negative feedback makes the OpAmp input voltages and - equal to each other within the linear range - Inverting Amplifier in t out in i in - A inv i in in The output signal is inverted with respect to input: ϕ 8 Limited input impeadance in out
in Non-inverting Amplifier out t in out - in - out A out non inv in The output and the input signals have the same phases: ϕ High input impeadance in
oltage Gain of Op-Amp with feedback Inverting configuration Non-inverting configuration KCL: i OUT i i B i OUT i i B OUT OUT i OUT B i OUT B i i B i i B OUT i - i OUT i - i OUT OUT B OUT A OUT A OUT
OpAmp Applications Analog integrator C i _ i C irtual GND KCL: i i C In the time domain: C t In the frequency domain: O ( t) C t ( t) dt jωc T O ( ω) j jωc ωτ
Active low-pass filter i _ C i Z jωc irtual GND KCL: i i Transfer function: Z O T ( ω) O Z jω C Magnitude response: Cut-off frequency: T ( ω) ω ω 2 f [ Hz] ω 2π 2πτ 2π C
Analog differentiator i C _ i irtual GND KCL: i i In the time domain: C t O ( t) In the frequency domain: O C t jω C O T ( ω) jωc jωτ
Active high-pass filter Z jωc C i _ i irtual GND KCL: i i Transfer function: T ( ω) O Z jω C Magnitude response: Cut-on frequency: f [ Hz] ω 2π 2πτ 2π C Z T ( ω) ω ω 2
Inverting summer KCL: i i 2 i 2 2 2 i i 2 2 irtual GND _ I 2 2 If 2 then - ( 2 )
Logarithmic amplifier KCL: i i D I exp O T D i D 2 _ i D irtual GND T ln I, < T ln I, > T T ln const ( ln ( I ) )
Exponential amplifier KCL: i D i I exp T O D i D D 2 _ i irtual GND I exp T exp( T ) I const exp ( )