## Unidirectional Diode Gate

A unidirectional diode gate which transmits only the positive - going input signals as shown in below figure. The gate signal which determines the gating or transmission period is a rectangular waveform that makes abrupt transitions between the two negative level -v_1 and -v_2 The gate signal is also called a control pulse, a selector pulse or an enabling pulse.When the gating signal is at its lower level -V2, the diode is heavily back biased and there will be no output due to the peak amplitude of the input signal is larger than the magnitude of this back-biasing voltage.When the gate signal is at its upper level   -V2, a time-coincident signal input pulse may be transmitted to the output.The gating effect of the upper level of the gating signal on the output is illustrated in the figure. The input is +10 v pulse.  In figure (a), when the gate pulse has –v2 = -20v and –v1 = -10v, there is no output pulse at...

## Basic operating principles of Sampling Gates

The basic operating principles of a sampling gates are illustrated in figures (a) and (b).a) Series Switch.b) Shunt Switch. In figure (a) the switch is normally open, but is in closed position when the signal is transmitted.In figure (b) the switch is normally closed, but is in open position when the signal is transmitted.These switches are normally electronic-devices diodes or transistors.When the device is conducting , it acts as a closed switch and when the device is not conducting, it acts as an open switch.Ideally a closed switch should have zero resistance and an open switch should have infinite resistance.But semiconductor devices do not have infinite back resistance and their forward resistances may lie in the range of several ohms.When such devices are used as switches, there is no specific advantages of either the series or the shunt switch position.The choice of the circuit depends upon the particular application....

## Managerial Skills

It is of three types. They are: Conceptual Skills  Human Skills  Technical Skills  Conceptual Skills: It is referred to as creative ability. It should be passed by top level management as the top level management involve in decision making of an industry. Conceptual skills includes knowledge about the product to be produced. It's marketing and financing and to look after weather the production is able to meet the required demand. Human Skills: It is primarily concerned with working by people. For the process of production, leadership, motivation, super vision, co-ordinations, control of workers is required. This skills are passed by all levels of management. As at each and every level it involve in a group. Technical Skills:  It refers to the proficiency in handling methods and process techniques of a particular kind of activity. This is very much needed in lower levels of the management. Brief description of management levels...

## Stability of An Op-Amp:

Consider an op-amp with negative feedback which uses a feedback resistor network which may be used as an inverting amplifier for V­­2 = 0 and non-inverting amplifier V1 = 0 The closed loop transfer function is given by ACL = A/1+Aβ Where; A : open loop voltage gain                B : Feedback ratio If (1+Aβ) = 0 the circuit will become unstable and gives sustained oscillations. Re-writing 1+Aβ = 0 as 1-(-Aβ) = 0 leads to –Aβ = 1 Aβ is a complex quality Therefore, │Aβ│ = 1 and phase condition Lle- Aβ =0 or (multiple of 2π)                                                                           Lle- Aβ =1 or (multiple of π)   Since, resistor is the present in feedback network it does't provide any phase shift. When op-amp is used in inverting mode it provides phase shift  Of 180o and at low frequencies. However at high frequencies due to each corner frequency an additional phase shift of maximum -90o can take place in open loop gain phase. So, for two corner frequencies maximum phase shift is added Hence at...

## Thermal Drift

Bias Current, Offset current, offset voltage change with temperature then a circuit is maintained at 250 room temperature. It does not remain so, and temperature raises to 350 which is called as drift. Usually current drift is expressed in nA/0c where offset voltage drift is expressed in mv/0c.Effect of thermal drift is minimized by cooling or placing PCV away from heat           ...

## Input offset voltage

Inspite of all the compensation techniques the output voltage is still not zero with zero input voltage.  Hence a small voltage is applied at the input terminals to make output voltage zero which is called as input offset voltage. The following are the non-inverting and inverting amplifiers respectively: Where  V1 =0 gives Voltage V2 is given by    V2 = V0 [R1/(R1+ Rf)] Or  V0 = V2 [ (R1+ Rf)/ R1] Since, Vios = │V1 – V2│and Vi = 0 Vios = │0 – V2│ =  V2 V0 = [1+(Rf/R1)] Vios...

## Characteristics of Op-amp

The non- ideal characteristics of op-amp which are DC and AC are:DC error components are:input bias current input offset current input offset voltage thermal driftInput Bias Current:The input bias current of an operational amplifier is the average of the two currents flowing at the inverting and non-inverting terminal respectively. The mathematical equation is given by:         IB = (IB++IB-)/2 For a Basic inverting op-amp : basic inverting op-amp If V1 = 0, then output voltage is offset given by,                V0 = IB - Rf1For 741 op-amp, Rf  = 1mΩ and input bias current is 500mA or less.Therefore, output voltage is driven to 500mV.In applications where signal levels are measure in milli-volts it is totally unacceptable. Hence, a compensated resistor is added between non-inverting input terminal and ground. Current IB+ going through the compensator resistor has a voltage V1 across itFrom KVL,-V1 + 0 + V2 – V0 = 0By selecting proper value of Rcomp V2 and be cancelled with V1 to make V0 Therefore, V1...

## Conditions of an Ideal Operational Amplifier

An op-amp is said to be ideal if it has the following characteristics. Open loop voltage gain (AOL) is infinity. Input resistance (Ri) is infinity. Output resistance (Ro) is zero. Bandwidth (BW) is infinity. Zero off-set (i.e) V0 = 0, when V1 = 0 & V2 = 0. An ideal op-amp cross no current and both the input terminal i 1 = i2 = 0. Because gain is infinite the voltage between inverting and non-inverting terminals i.e op-amp is essentially zero for infinite output voltage V0 is independent of the current drawn from the output is R0 = 0....