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Log circuit op-amp

EC.24)Identify the op-amp circuit above and define the relationship between the input and output voltage ,given the diode-current voltage :i_D =I_S(e^{[qv_D/kT]} -1).Here, I_S is a constant dependent on diode construction.
q is electron charge
k is Boltzmann's constant
T is absolute temperature.
Then,v_i at the input equals
(a)-RI_S(e^{[qv_o/kT]} -1)
(b)-RI_S(e^{[-qv_o/kT]} +1)
(c)R/I_S(e^{[qv_o/kT]})
(d)insufficient data,cannot be determined

Answer is (a)
The voltage at inverting input can be neglected such that the output voltage equals the diode voltage.Under this condition, i_D and i_R sum to zero i.e., i_D + i_R = 0 ,\implies i_R=-i_D
i_R = v_i/R, \implies v_i = -Ri_D
\therefore v_i = -RI_S(e^{[qv_D/kT]} -1)