The fundamental factors which determine the characteristics of a (n⁺-p-n⁺)-n⁺ device are the applied voltage and illuminated light (L). Besides these factors, the characteristics of the device are influenced by external factors such as capacitance, resistance and auxiliary voltage. When a capacitance C is added between the main and auxiliary electrodes, , decrease of the frequency and the threshold voltage of oscillation, and increase of the output pulse current occur. The frequency ƒ is expressed as ƒ=a•C^-k•Lⁿ and the pulse width τ as τ=b•C+τ₀. Connection of a resistance R increases the frequency. When an R-C parallel circuit is added, the minimum frequency ƒ_min is determined by the value of C, and the frequency increases up to 50_??_60 times of ƒ_min with decrease of R. Addition of an auxiliary voltage V₁ decreases the threshold voltage of oscillation and increases the frequency.