Govt. Exams
Entrance Exams
Bandwidth of a low-pass filter is defined by its cutoff frequency (-3dB point). At f = fc, magnitude drops to 0.707 of DC gain. Bandwidth = fc = 1 kHz.
The 741 op-amp has a gain-bandwidth product of approximately 1 MHz. This means for a gain of 100 V/V, maximum usable bandwidth is ~10 kHz.
The 741 op-amp has a slew rate of approximately 0.5 V/μs. This limits the maximum output voltage change rate, causing distortion at high frequencies/amplitudes.
Precision op-amps like OP07, OPA2134 are designed with input offset voltages < 1 mV. General purpose op-amps (e.g., 741) have offset voltages of 1-5 mV.
Maximum power transfer theorem states that maximum power is delivered when load impedance equals the complex conjugate of source impedance. For resistive cases, RL = Rs.
An ideal op-amp has infinite input impedance. The voltage follower configuration maintains this high input impedance at the non-inverting input.
Output current Id = gm × Vgs = 50 mS × 10 mV = 50 × 10⁻³ × 10 × 10⁻³ = 0.5 × 10⁻³ A = 0.5 mA
In cascaded amplifiers, overall voltage gain = A₁ × A₂ = 50 × 20 = 1000. The bandwidth is determined by the stage with lowest bandwidth (100 kHz).
In saturation, both junctions are forward biased: base-emitter junction is forward biased for current conduction, and base-collector junction is also forward biased, allowing maximum collector current.
Darlington pairs consist of two transistors in cascade, providing extremely high current gain (β² product) and very high input impedance due to the two base-emitter junctions.
