For the operational amplifier circuit shown, the output saturation voltages are $$ \pm \,\,15V$$. The upper and lower threshold voltages for the circuit are, respectively.

The following signal V_i of peak voltage 8V is applied to the non-inverting terminal of an ideal Opamp. The transistor has V_BE = 0.7 V, $$\beta \, = \,100;$$ V_LED = 1.5 V, V_CC = 10V and -V_CC = -10V.

The number of times the LED glows is ______.

Consider the constant current source shown in the figure below. Let $$\beta $$ represent the current gain of the transistor

The load current I₀ through R_L is

In the bistable circuit shown, the ideal opamp has saturation levels of $$ \pm 5V.$$ The value of R₁ (in k$$\Omega $$ ) that gives a hystersis width of 500 mV is ______