ECE 3201 - BJT

You can achieve a current gain greater than beta (T/F)

False

For a NPN transistor, it will be in forward active region if (?). What about PNP?

Forward active if Vce is greater than 0V but less than Vcc. (NPN) Forward active if Vce is less than 0V but greater than Vee (PNP)

Ratio of R1 and R2 (for design)

Vcc - (Ve + Vbe) / (Ve + Vbe)

What type of circuit is this?

Voltage Divider Bias

What type of circuit is this?

Voltage Feedback Bias

Voltage Swing and Current Swing

Voltage Swing = min {2(Vceq), 2(Vceo - Vceq)} Current Swing = Voltage Swing / RL

Common Base Bias

What type of circuit is this?

Emitter-Stabilized Bias

What type of circuit is this?

Fixed Bias

What type of circuit is this?

For an emitter follower, Ro is approximately equal to (?)

re

How do you find Ai1, Ai2, and AiT?

Ai1 = -Av1(Ri1 / Ri2) Ai2 = -Av2(Ri2 / RL) AiT = -AvT(Ri1/RL)

When considering a two cascaded amplifier, how do you find Av1? Av2? Avt? Avts?

Av1 = Avnl1 (Ri2 / Ri2 + Ro1) Av2 = Avnl2 (Rl / Rl + Ro2) Avt = Av1 * Av2 Avts = Avt * (Ri1 / Ri1 + Rsig)

Rank the voltage gain from least to greatest (with load and ac signal input, with load, without load)

Avs, Av, Avnl

Draw a CE amplifier with unbypassed RE ac small signal model

Draw

Draw a EF/CC ac small signal model

Draw

Draw a common base amplifier ac small signal model

Draw

Draw a fixed bias CE ac small signal model

Draw

Draw a voltage divider CE ac small signal model

Draw

The voltage divider bias circuit is the least susceptible to changes with respect to Beta (T/F)

True

AC Load Line

(Ic - Icq) = -1/(Rc || RL) * (Vce - Vceq)

What does it mean when transistor is at cutoff?

Currents are 0

Describe the voltage gain for common emitter, common base, and common collector

CE = high and inverting (-100) CB = high (100) CC = unity and inverting (-1)

Describe the input impedance for common emitter, common base, and common collector

CE = moderate (1k ohms) CB = low (10 ohms) CC = high (100k ohms)

Describe the output impedance for common emitter, common base, and common collector

CE = moderate (1k ohms) CB = moderate (1k ohms) CC = low (10 ohms)

What type of circuit is this?

Collector Feedback CE

What type of circuit is this? (Ignore R2)

Common Collector/Emitter Follower Amplifier

In a Q point graph, if you increase Ib, where would the Q point go? Increasing beta? Increasing Rc? Decreasing Vcc?

Q point will go upward, more to the left Q point will go upward, more to the left (depending on the beta value) Q point would shift downward, due to a new load line (y-intercept decreases) Q point would shift downward, where new line changes (shift downward)

A circuit is sensitive to beta if (?) A circuit is sensitive to Vbe if (?)

R1 + R2 (Rth) >> RE If both Rth and Re are small

For a NPN transistor, it will be in saturation if (?). What about PNP?

Saturated if Vce is less than 0V (NPN) Saturated if Vce is greater than 0V (PNP)

In a Q point graph, if a point is near the y-axis, what does that mean? What about x-axis?

Y-axis = limited voltage swing X-axis = limited current swing

Rank the circuit that is sensitive to beta from least to most (voltage divider, fixed bias, emitter stabilized)

voltage divider emitter stabilized fixed bias