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 ______.

In the circuit shown using am ideal opamp, the 3-dB cut-off frequency (in Hz) 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 ______

In the circuit shown, V_O = V_OA for switch SW in position A and V₀= V_OB for SW in position B. Assume that the opamp is ideal.

The value of $${{{V_{OB}}} \over {{V_{OA}}}}$$ is _____