Three identical inverters are used to make a ring oscillator

Three identical inverters are used to make a ring oscillator as shown below, a) Find the input capacitance per gate, b) Estimate the rise and fall times for each of the inverters, assuming a load equal to C_In and abrupt transitions at the input and output, c) Assuming that each gate experiences input rise and fall times equal to the values determined in the previous part, estimate the propagation delays and the frequency of oscillation for the ring oscillator.

Solution

a) C = L* ephsilon/t

= 0.1* 8.85* 10-¹² / 10

= 58.5 micro farad

b) rise time = C* Vt/ i

= 58.5 * .5 / 8

= 10.25 sec

c) Tr = tF = 10.25 sec