high power grounded grid triode amplifier
TRANSCRIPT
SUMMER INTERNSHIPREPORT
ANALYSIS OF A HIGH POWER GROUNDED
GRID TRIODE AMPLIFIER… … … … … … … … … … … … … … … … … … … … … … … … … … .
VARIABLE ENERGY CYCLOTRON CENTER - KOLKATA
WHAT IS AMPLIFIER
AMPLIFIER :An amplifier is an electronics device that increases voltages ,current and power of a signal.
According to class of operation amplifiers are classified as :
1. Class A2. CLASS B3. CLASS AB4. CLASS C
CLASS A :
A class A amplifier is one in which the operating point and the input signal are such that the current in the output circuit flows at full times.
The output signal of class A amplifiers varies for a full 360o of the cycle.
CLASS B :
A class B amplifier is one in which the operating point is at an extreme end of its characteristic, so that the quiescent power is very small. If the signal voltage is sinusoidal, amplification takes place for only one-half a cycle.
A class B circuit provides an output signal varying over one-half the input signal cycle, of for 180o of input signal.
CLASS AB :
A class AB amplifier is one operating between the two extremes defined for class A and class B. Hence the output signal is zero for part but less than one-half of an input sinusoidal signal.
For class AB operation the output signal swing occurs between 180o and 360o and is neither class A nor class B operation.
Class C:
A class C amplifier is one in which the operating point is chosen so that the output current (or voltage) is zero for more than one-half of the input sinusoidal signal cycle.The output of a class C amplifier is biased for operation at less than 180o of the cycle and will operate only with a tuned (resonant) circuit which provides a full cycle of operation for the tuned or resonant frequency.
SOLID STATE AMPLIFIERS :
Advantages
• Solid state amplifiers are generally smaller than equivalent tubes and consume low power in small signal circuits
• Less waste of heat than equivalent tubes.• Matching transformers are not required for low input impedances.• Can operate at low voltage supply , greater safety and lower components costs.• Can b combined in one die to make integrated circuits. • Usually more physical ruggedness than tubes (depends on chassis construction)Disadvantages:
• Tendency toward higher distortion than equivalent tubes• Complex circuits and considerable negative feedback
required for low Distortion• Device capacitances tend to vary with applied voltages• Large unit-to-unit variations in key parameters, such as
gain and threshold voltage• Device parameters vary considerably with temperature,
complicating biasing and raising the possibility of thermal runaway• Less tolerant of overloads and voltage spikes than tubes• Capacitive coupling usually requires high-value
electrolytic capacitors
ANALYSIS OF SOLID STATE AMPLIFIER
The above graph shows the input versus output plot. For a certain range of input, the graph is exponentially increasing in nature.
The above graph depicts the output versus frequency plot at a fixed input of 4.10 dBm. The output is maximum for the frequency of 7 MHz.
TUBE AMPLIFIER :Triode amplifier’s working is similar to that of n- channel JFET but unlike FET which is current dependent device triodes are voltage dependent device . It has 3 major components :
1. Cathode 2. Grid 3. Plate
Here cathode is heated using a filament ,which is supplied with external power , to generate electrons . When grid voltage is greater than the cathode voltage electrons flow in the tube.So grid voltage controls the outflow of electrons from cathode to plate.
Fig . Showing Triode Schematic
Fig . Showing working of a triode
Why Use Tube Amplifiers
• ADVANTAGES
• Highly linear without negative feedback, specially some small-signal types• Clipping is smooth, which is widely considered more musical than transistors• Characteristics highly independent of temperature, greatly simplifies biasing• Wider dynamic range than typical transistor circuits, thanks to higher operating voltages• Device capacitances vary only slightly with signal voltages• Capacitive coupling can be done with low-value, high-quality film capacitors• Circuit designs tend to be simpler than semiconductor equivalents• Operation is usually in Class A or AB, which minimizes crossover Distortion
DISADVANTAGES• Bulky, hence less suitable for portable products• High operating voltages required• High power consumption, needs heater supply• Generate lots of waste heat• Lower power efficiency than transistors in small-signal circuits• Low-cost glass tubes are physically fragile• Cathode electron-emitting materials are used up in operation, resulting in shorter lifetimes (typically
1-5 years for power tubes)• High-impedance devices that usually need a matching transformer for low impedance loads, like
speakers• Usually higher cost than equivalent transistors
ANALYSIS OF SSA DRIVEN TRIODE AMPLIFIER
32.3
35.538.
9142.
27 45.548.
54 51.454.
0656.
4558.
7160.
7261.
77 6262.
1702468
1012141618
Gain
Gain
16.02
23.72
931.
4637.
7843.
1347.
8750.
230
10203040506070
Output(dBm)
Output(dBm)
32.335.
538.
9142.
2745.548.
5451.454.
0656.
4558.
7160.
7261.
77 6262.
1705
101520253035404550
Efficiency
Efficiency
DC ANALYSIS OF AMPLIFIER
The above graph depicts plate voltage and plate current for different value of grid voltages. For a fixed grid voltage, on increasing the voltage, the plate current will increase. This is because more electrons get pulled towards the plate. Also, on increasing grid voltage due to a similar effect, the plate current will increase. The slope of the above graph gives the value of trans conductance.
• Amplification Factor : 6.44• Plate Resistance (rp) : 57.27 KOhm• Transconductance (gm) : . 17 mS
COMPLETE ANALYSIS
INPUT-OUTPUT PLOT
-20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 120
10
20
30
40
50
60
70Output(dBm)
Output(dBm)
Input (dBm) Output(dBm)-20 32.205-18 35.65-16 39.041-14 42.44-12 45.67-10 48.7
-8 51.59-6 54.29-4 56.65-2 58.92
0 60.942 62.014 62.286 62.468 62.61
12 62.92
The input versus output plot is depicted in the above figure. As we increase the input the output increases and becomes almost constant.
EFFICIENCY
32.20535.6539.04142.44 45.67 48.7 51.59 54.29 56.65 58.92 60.94 62.01 62.28 62.46 62.61 62.920
10
20
30
40
50
60 Efficiency
Efficiency
Output(dBm) Efficiency32.205 0.101
35.65 0.2139.041 0.46
42.44 1.0145.67 2.1
48.7 4.1651.59 7.8354.29 13.5756.65 20.4958.92 29.2260.94 37.662.01 42.7662.28 45.0762.46 46.1362.61 47.4962.92 49
The efficiency of the complete system is shown above. Efficiency goes on increasing with output.
GAIN
32.20
535.
6539.
041
42.44
45.67 48.
751.
5954.
2956.
6558.
9260.
9462.
0162.
2862.
4662.
6162.
920
10
20
30
40
50
60
70
80
Gain (dBm)
Gain (dBm)
Output(dBm) Gain (dBm)32.205 52.405
35.65 53.6539.041 55.041
42.44 56.4445.67 57.67
48.7 58.751.59 59.5954.29 60.2656.65 60.8558.92 60.9960.94 60.9462.01 64.0162.28 66.2862.46 68.4662.61 70.6162.92 74.92
Gain is the measure of amount of amplification of input power resulting in output power. The gain of the complete system comes out to be maximum at 62.92 dBm.
HARMONICS 2
32.20
535.
6539.
041
42.44
45.67 48.
751.
5954.
2956.
6558.
9260.
9462.
0162.
2862.
4662.
6162.
92
-80
-70
-60
-50
-40
-30
-20
-10
0
Harmonis 2 with respect to harmonics 1
Harmonis 1
Output(dBm) Harmonis 132.205 -71.86
35.65 -69.5939.041 -71.86
42.44 -70.7845.67 -67.18
48.7 -70.4851.59 -7154.29 -61.5556.65 -56.558.92 -56.9660.94 -58.362.01 -58.662.28 -57.7662.46 -58.162.61 -57.262.92 -57.86
HARMONICS 332.
205
35.65
39.04
142.
4445.
67 48.7
51.59
54.29
56.65
58.92
60.94
62.01
62.28
62.46
62.61
62.92
-80
-70
-60
-50
-40
-30
-20
-10
0
Harmonics3 with respect to Harmonics 1
Harmonics 2
Output(dBm) Harmonics 2
32.205 -72.67
35.65 -70.05
39.041 -74.55
42.44 -73.65
45.67 -69.5
48.7 -72.48
51.59 -72.8
54.29 -65.95
56.65 -63.6
58.92 -60.05
60.94 -59.1
62.01 -71.1
62.28 -58.06
62.46 -60.3
62.61 -58.35
62.92 -57.9
PROJECT WORK UNDER GUIDANCE OF :
HEMENDRA KUMAR PANDEYSCIENTIFIC OFFICERRIB LABVECC,KOLKATA
PROJECT INTERNS :
VISHAL ANAND SAURABH SATYAM NIT- PATNA NIT-PATNA
