In the circuit for relaxation oscillator, with R_BB = 5 kΩ, η = 0.6, V_v = 1 V, I_v = 10 mA and I_p = 10 μA, the value of R_B1 is:

Concept:

UJT Relaxation Oscillator:

The Unijunction Transistor or UJT for short is another solid-state three-terminal device that can be used in gate pulse, timing circuits, and trigger generator applications to switch and control either thyristors and triac’s for AC power control type applications.

Here;

R_BB = R_B1 + R_B2

η = R_B1/(RB1 + RB2)

Calculation:

RBB = 5 kΩ 

η = 0.6 

Vv = 1 V 

Iv = 10 mA

Ip = 10 μA 

Then;

η = RB1/(RB1 + RB2) = η = RB1/R_BB

∴ R_B1 = ηR_BB = 0.6 × 5 = 3 kΩ