Which one of the following has the shortest access time?

This question was previously asked in
ESE Electronics 2010 Paper 2: Official Paper
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  1. NMOS EPROM
  2. NMOS RAM
  3. CMOS RAM
  4. Bipolar static RAM

Answer (Detailed Solution Below)

Option 4 : Bipolar static RAM
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ST 1: UPSC ESE (IES) Civil - Building Materials
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Detailed Solution

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MOSFETs are slower than BJTs because of enormous capacitances at their junctions, formed by metal, substrate and the oxide layer.

Due to the high value of capacitances time constant(T=RC) of MOSFET is high and has a lower switching speed in comparison to BJT. Hence Bipolar static RAM will have the shortest access time.

NOTE-

We Generally use MOSFETs in digital circuits because of their low power to switch( gate current = 0 almost), lesser static power dissipation, ease of fabrication, thermal stability, and less leakage (only the majority of carriers form the current in MOSFET).

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