11815195
Description
Flashcards by Steven Pearson, updated more than 1 year ago
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Created by Steven Pearson
about 7 years ago
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| Question | Answer |
| how many types of active devices are there? what are they called? | 2 mosfet and BJT |
| 1) Draw the structure of a MOSFET 2) Draw the symbols for the two types of MOSFET | structure --- symbols - pMOS & nMOS |
| 1) Draw the structure for a BJT 2) Draw the symbols for the two types of BJT's | structure --- symbols - NPN & PNP |
| what does MOSFET stand for? | Metal Oxide Silicon Field Effect Transistor |
| 1) How many operation regions are there for BJT and MOSFET and what are they called? 2) Draw The output characteristics | There are 3 regions Triode Active Off |
| Draw the equivalent band model for a MOSFET device at mid-band frequency | |
| Draw the equivalent band model for a BJT device at mid-band frequency | |
| With the aid of the MOSFET’s structure, explain the origin of the parasitic capacitor. At what operating conditions will these capacitors start to play an important role, why? | When at high frequency, these parasitic capacitors become important, because these capacitors are very small. Z = 1/(2*pi*f*C) |
| With the aid of the BJT's structure, explain the origin of the parasitic capacitor. At what operating conditions will these capacitors start to play an important role, why? | ???? |
| Draw the equivalent band model for a MOSFET device at high-band frequency | ?? |
| Draw the equivalent band model for a BJT device at high-band frequency | ?? |
| list the Major differences between MOSFET and BJT | 1) BJT is three terminal device, while MOSFET is four terminal device. 2) BJT is a current-controlled device where the collector or emitter output is a function of the current in the base. MOSFET is a voltage-controlled device. There is no base current present. 3)The input of a typical BJT has a pn junction, while for MOSFETs, they are insulated. |
| what is also known as a DC Bias Point and what is it used for | The Q-point Its used to set a mosfet in its saturation region for signal amplification |
| what is the equation for Id current of a MOSFET whilst in the active region? | Id = K*( Vg-Vt )^2 |
| how do you double check that the MOSFET is in the Active reigion? | Vd: Vdd - Id * Rd ensure that this value is greater than Vt (the threshold voltage) |
| what is the equation for calculating RD over a mosfet? | RD = ( VDD - VD ) / ID |
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how do you add coupling capacitors in to this circuit?
and what is the function of them?
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AC ==> DC
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| what is the equation for calculating Impedance ( Z ) ? + rearrange this equation to find frequency ( F ) ? | Z = 1 / (2 * PI * F * C) F = 1 / ( 2 * PI * C * Z |
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convert this circuit to its ac equivalent
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what are the golden rules?
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how do you check the circuit is really equivalent?
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how do you calculate resistors in parallel?
eg: R1 & R2
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R1 x R2 / (R1 + R2) |
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Draw equivalent circuit at high-band.
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| what does A stand for? | A stands for voltage gain |
| how is GM calculated over a mosfet AC equivalent circuit? - the equation | GM= -A / Rd gm is calculated by -gain / Rd |
| what is the equation for calculating gain (A) over a mosfet device? | A = -gm x Rd or A = Vout / Vin |
| what is the formula for GM when gm and A are not given? | GM = 2K * ( vg - vt ) |
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| how is Rin calcualted? | Rin = Vin / Iin |
| what is the formula for critical frequency? | f = 1/ 2 * PI * R * C |
| what is a bypass capacitor and what is are coupling capacitors? | Bpass - used to force signal around elements by providing a low impedance path. Coupling - used to decouple ac and dc signals which do not disturb the Qpoint. |
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