Electronic Circuits - Part3: Bipolar Junction Transistors

Explore structure of the bipolar junction transistor, detailing emitter, base, and collector roles. See how base-emitter forward bias and base-collector reverse bias drive current and how α and β relate.

Analyze how forward-biasing the base-emitter and reverse-biasing the base-collector governs emitter, base, and collector currents, with alpha, leakage ICO, and is-based exponential equations for NPN and PNP transistors.

Explore how base current and collector-emitter voltage shape common-emitter BJT output characteristics, revealing cutoff, saturation, and active regions, and explain leakage currents ICO/ICEO and the Early effect.

Compute currents and gains in common-base BJTs, using α and β with leakage (ICBO, ICEO), apply KCL and Ohm's law, and determine base and emitter-base voltages and breakdowns.

Explore the common-collector (emitter follower) configuration where input at the base drives the emitter output and the emitter voltage tracks the base voltage, yielding a current gain of about β+1.

Analyze dc operation of a bjt in forward active region using a large-signal model; determine base, collector, and emitter currents and voltages via kvl and thevenin reduction.

Examine a DTL-based digital NAND gate, analyze currents and voltages for four input cases, and explore transistor saturation, diode-connected transistors, and TTL implementations.

Analyze dc biasing of a bipolar junction transistor using a current source, determine collector current and voltages, identify saturation, and explore current-mirror and Wilson current source designs for bias stability.

Analyze a pair of identical transistors in a parallel push-pull circuit with IC 1.2 mA, derive VB from Vbe 753 mV, and examine β.

Integrated circuit biasing uses transistors as current sources to fix emitter and collector currents, independent of beta. The lecture designs a two-transistor current source biased at 0.2 mA.

Apply load-line analysis to bias a transistor for maximum gain or maximum output swing in a common-emitter circuit, balancing DC and AC considerations to avoid cutoff and saturation.

Determine the operating point and dc output voltage from dc analysis, then analyze ac swing with the ac load line and a gain of 80, yielding 25 mv clipping limit.

Analyze the dc operating point and ac analysis of BJT amplifiers, focusing on common-emitter configurations, voltage and current gain, input and output resistances, and hybrid-pi modeling.

Design two common-emitter amplifier examples to meet current gain above 110, input resistance above 1.5 kΩ, and at least 1 V symmetrical output swing, with biasing and Thevenin resistance considerations.

Calculate voltage and current gain of a common-emitter with emitter degeneration using the t-model, relating VB, Vπ, and Vs via careful input-resistance and voltage-divider analysis.

Analyze emitter follower in a BJT circuit, deriving input and output resistances and voltage and current gains via dc and small-signal analysis, with 0.98 voltage gain and 58.3 current gain.

Explore how to determine the output resistance of current sources, from two- and three-transistor configurations to cascode and Widlar designs, using small-signal analysis.

Compute dc base and collector voltages and voltage gain Vo/Vs in a common-emitter BJT circuit, using gm, rπ, ro for ac analysis, with Ic equals -VEE/(2RE) when neglecting base current.

Explains ac coupled multistage amplifiers and how the loading between two common-emitter stages shapes the overall gain, with remedies like high input impedance or a common-collector stage.

Design a multistage bipolar junction transistor amplifier to achieve a gain greater than 8000 with a 5 V supply, using emitter followers for buffering and biasing for maximum output swing.

Calculate the voltage gain and input and output resistances for a common-emitter amplifier with emitter degeneration, using rπ and reflected RE(β+1), where output resistance sums T2’s emitter and T1’s output.

Learn to read transistor datasheets to identify terminals and evaluate maximum ratings, leakage currents, and current gain β for accurate circuit design, including saturation voltage and VCEO.

Use a BJT level detector that saturates to light an LED when liquid reaches the probes. Adjust base current with a potentiometer, and use a 150 ohm collector resistor.

Explains driving an 8Ω speaker from a bjt amplifier by adding an emitter follower output to recover gain and raise input impedance, with biasing and base resistor calculations.

Set up a BJT circuit in Multisim for DC and AC analysis, obtain a 0.99 mA operating point, and compute voltage gain as Vout over Vin with magnitude and phase.

Use Multisim to determine the input and output resistances of a multistage amplifier, comparing dc and ac analyses with dc and ac equivalents for Q1–Q4, and verify gain of 248.

Conclude this part on bipolar junction transistor circuits by encouraging you to build and analyse your own BJT project, applying transistor design and analysis skills to future courses.