In which of the following types of A/D converters does the conversion time almost double for every bit added to the device?

Concept:The conversion time of the countertype A/D counter is \((2^n - 1) T_ {clk}\)  1 bit =  \((​​2^1-1)T_{CLK}\) = \(T_{clk} \).

  2 bit = \((​​2^2-1)T_{CLK}\) = \(3T_{clk}\).

  From above when bit increases, conversion doubles, So the answer is counter type A/D converter.

Additional Information

• Dual slope A/D converter is \((2^{n+1}-1)T_{clk}\)
• Flash type A/D converter is \(T_{clk}\)
• Successive approximation type A/D converter is \(nT_{clk}\)

Important Points 

• Counter type ADC and successive approximate ADC uses DAC
• Counter type ADC uses linear search and successive approximation type ADC uses binary search
• Ring counter is used in successive approximation type ADC
• Flash type ADC is fastest ADC
• Flash type ADC requires no counter
• For an n-bit ADC, flash type ADC requires (2n – 1) comparators
• Dual slope ADC is most accurate