What is the condition called when a transistor in an amplifier is driven by the input signal to a point where the collector current becomes zero?
Explanation
When the input signal to a BJT amplifier causes the base current to drop to a level where the collector current also becomes zero, the transistor is said to be in cutoff. This represents one of the limits of linear operation, and if the signal swing drives the transistor into cutoff, the output waveform will be clipped.
Other questions
In the normal operation of a BJT as an amplifier, how are the base-collector and base-emitter junctions biased?
What is the relationship between the emitter current (iE), collector current (iC), and base current (iB) in a BJT according to Kirchhoff's current law?
The parameter beta (β) in a BJT is defined as the ratio of which two currents?
If a BJT has a current gain parameter alpha (α) of 0.99, what is the corresponding value of beta (β)?
In a BJT amplifier circuit, what term describes the operating point when the AC input signal is zero?
For a pnp BJT to operate as an amplifier, how must the polarities of the applied DC voltages compare to those of an npn BJT?
Which of the following describes the large-signal DC model for an npn BJT operating in the saturation region?
Why is the fixed base bias circuit generally considered unsuitable for mass-produced amplifiers?
In the DC analysis of a four-resistor BJT bias circuit, the voltage divider formed by R1 and R2 and the VCC supply can be replaced by what?
In a BJT small-signal equivalent circuit, what does the resistance r_pi represent?
For the midband small-signal AC analysis of a BJT amplifier, how are DC voltage sources and coupling capacitors typically treated?
What is the key characteristic of the output voltage of a common-emitter amplifier relative to its input voltage?
Which BJT amplifier configuration is characterized by a voltage gain slightly less than unity, high input impedance, and low output impedance?
What is the reason for the name 'emitter follower' for the common-collector amplifier?
Consider the fixed base bias circuit shown in Figure 12.18(a) with RB = 200 kOhm, RC = 1 kOhm, VCC = 15 V, and a transistor with beta = 100. What are the calculated values for the DC collector current (IC) and collector-emitter voltage (VCE)?
In the load-line analysis of the BJT amplifier in Example 12.2, with VCC = 10 V and RC = 2 kOhm, what is the value of the collector current when the transistor is in cutoff?
What is the small-signal resistance r_pi for a BJT with beta = 100 and a quiescent collector current ICQ = 1 mA, assuming a thermal voltage VT of 26 mV?
In the common-emitter amplifier of Example 12.8, with RB = 3.33 kOhm, r_pi = 631 Ohm, and RL_prime = 667 Ohm, what is the calculated input impedance Zin?
For the common-emitter amplifier in Example 12.8, the calculated voltage gain Av is -106. If the input source vs(t) is 0.001 sin(vt) and the source resistance Rs is 500 Ohm, what is the approximate output voltage vo(t)? Note that Zin = 531 Ohm.
In the analysis of the four-resistor bias circuit in Example 12.7, what are the Thévenin voltage VB and Thévenin resistance RB for VCC = +15 V, R1 = 10 kOhm, and R2 = 5 kOhm?
What is the primary cause of nonlinear distortion in a BJT amplifier when it is operating within the active region?
In a pnp BJT circuit symbol, which way does the arrow on the emitter terminal point?
According to the step-by-step procedure for DC analysis of BJT circuits, what is the first step?
What is the purpose of the bypass capacitor CE in a common-emitter amplifier like the one in Figure 12.27(a)?
In the small-signal equivalent circuit for a common-emitter amplifier, why is the resistor R1, which is connected to VCC in the actual circuit, shown connected from the base to ground?
What is the formula for the open-circuit voltage gain (Avoc) of the common-emitter amplifier shown in Figure 12.27?
What is the output impedance (Zo) of the common-emitter amplifier shown in Figure 12.27?
A transistor has iC = 9.5 mA and iE = 10 mA. What are the values of its base current iB and current gain beta?
For the emitter follower circuit of Example 12.9, what is the calculated voltage gain Av, given r_pi = 1260 Ohm, beta = 200, and the effective load R'L = 667 Ohm?
What is the key advantage of the four-resistor bias circuit over the fixed base bias circuit regarding the operating point?
In the small-signal equivalent circuit of an emitter follower (common-collector amplifier), the collector terminal is connected to what?
A simple BJT amplifier circuit is shown in Figure 12.7. If the input signal vin(t) swings positive, what is the effect on the base current iB and the collector-emitter voltage vCE?
A BJT is in the saturation region when vCE is approximately 0.2 V. What does this condition indicate about the two junctions of the BJT?
In the large-signal DC model for a BJT, the cutoff region is characterized by what condition?
A BJT amplifier has a quiescent collector current ICQ of 2.13 mA when beta is 100. If beta changes to 300, the collector current becomes 2.14 mA. Which bias circuit is most likely being used?
What is the primary reason an emitter follower amplifier is used in circuit design?
In the small-signal model of a BJT, the relationship between the small-signal collector current (ic) and the small-signal base current (ib) is given by what equation?
For the emitter follower analysis in Section 12.9, what is the input impedance seen looking into the base of the transistor (Zit)?
A certain npn transistor has VBE = 0.7 V for IE = 20 mA. Using the Shockley equation and assuming VT = 26 mV, what is the approximate VBE for IE = 2 mA?
The common-emitter input characteristic, as shown in Figure 12.5(a), is a plot of what two quantities?
What does the fluid-flow analogy for a BJT compare the base current to?
In the load-line analysis of a common-emitter amplifier, what determines the slope of the input load line?
Consider the circuit in Figure 12.23, which is used in Example 12.7. For a transistor with beta = 300, what is the calculated collector current IC?
Even though the voltage gain of an emitter follower is less than unity, why is it still considered an effective amplifier?
For the emitter follower circuit in Example 12.9, what is the calculated current gain Ai, given Av = 0.991, Zin = 36.5 kOhm, and RL = 1 kOhm?
If a BJT's alpha (α) is 0.95, what is its beta (β)?
In a simple BJT amplifier circuit like the one in Figure 12.7, if the DC supply VCC is increased, how does the output load line on the iC-vCE characteristics change?
An npn BJT has a beta of 50. If the base current iB is 30 microA, what is the collector current iC, assuming the transistor is in the active region?
For the BJT amplifier in Example 12.2, with a Q-point at IBQ = 25 microA and VCEQ = 5 V, the input signal vin(t) causes the base current to swing between 15 microA and 35 microA. What are the corresponding minimum and maximum values for VCE?