Fundamentals of Electronics Flashcards

What type of feedback is used in most biomedical amplifier designs to stabilize gain and improve linearity?

Answer: Negative feedback

Negative feedback reduces gain but improves stability, linearity, bandwidth, and reduces distortion — essential characteristics for accurate biomedical signal amplification.

A defibrillator capacitor stores 360 joules at 5000 V. What is the capacitance value?

Answer: 28.8 µF

Energy E = ½CV², so C = 2E/V² = 2×360/(5000²) = 28.8 µF.

In a pulse oximeter, photodetectors measure light absorption at two wavelengths. Which wavelengths are typically used?

Answer: 660 nm and 940 nm

Pulse oximeters use red light (~660 nm) and infrared light (~940 nm) because oxyhemoglobin and deoxyhemoglobin have distinct absorption differences at these wavelengths.

What is the Nyquist theorem's requirement for sampling an analog signal to avoid aliasing?

Answer: Sample at least twice the highest frequency in the signal

The Nyquist theorem states that the sampling rate must be at least twice the highest frequency component of the signal to accurately reconstruct it without aliasing.

In a biomedical pressure transducer using a strain gauge, what electrical parameter changes in response to physical deformation?

Answer: Resistance

Strain gauges work on the piezoresistive principle — mechanical deformation changes the geometry of the conductor, altering its electrical resistance.

What is the function of a sample-and-hold circuit in an analog-to-digital conversion system?

Answer: Freezes the analog signal value during the ADC conversion period

A sample-and-hold circuit captures and maintains the analog input voltage constant during the ADC's conversion time, preventing errors from signal changes during conversion.

In medical electronics, what is the maximum allowable patient leakage current for a Type CF (cardiac floating) applied part under normal conditions per IEC 60601-1?

Answer: 10 µA

IEC 60601-1 limits patient leakage current for Type CF (cardiac floating) applied parts to 10 µA under normal conditions to protect against microshock hazards.