Amplifier JFET User Manual
Amplifier JFET User Online Manual This comprehensive digital guide provides step-by-step instructions for utilizing the Amplifier JFET software suite. Designed for electronics engineers and students, this manual covers everything from initial circuit configuration and biasing point (Q-point) analysis to advanced frequency response simulations. Master the art of Junction Field-Effect Transistor modeling with our interactive documentation.
Schematic diagrams of amplifier stages based on a junction field-effect transistor (JFET) are shown in Figure 1.
Figure 1 – Schematic diagrams of amplifier stages based on a junction field-effect transistor (JFET): a), c) common source (CS); b), d) common drain (CD)
Figure 1 – Schematic diagrams of amplifier stages based on a junction field-effect transistor (JFET): a), c) common source (CS); b), d) common drain (CD)
1. Selecting a transistor model from the database
Selecting the transistor model (see Figure 2).
Under the heading "Input transistor model", type the transistor model name in the input field using Latin characters (case-insensitive), as indicated by the arrow in Figure 2 above.
If the model is found in the database, it will appear in the list on the left under the "Model Search" heading. Once the model is located, you can proceed to calculate the amplifier. After entering the model name and confirming it is in the database, select the amplifier stage configuration to be calculated: common source (CS) or common drain (CD), as shown in Figure 3.
Under the heading "Input transistor model", type the transistor model name in the input field using Latin characters (case-insensitive), as indicated by the arrow in Figure 2 above.
If the model is found in the database, it will appear in the list on the left under the "Model Search" heading. Once the model is located, you can proceed to calculate the amplifier. After entering the model name and confirming it is in the database, select the amplifier stage configuration to be calculated: common source (CS) or common drain (CD), as shown in Figure 3.
Once the transistor model and amplifier stage configuration have been selected, perform the preliminary calculation. To do this, click the "Calculate" button located to the left of the transistor model input field, and the program will calculate the amplifier stage.
Note for step 1:
If the model is not found, you can search for transistor equivalents; it is quite possible they will be available in the program's database.
Note for step 1:
If the model is not found, you can search for transistor equivalents; it is quite possible they will be available in the program's database.
2. Preliminary calculation results for the amplifier stage
After clicking the "Calculate" button (see Figure 4 below), the program will calculate and display the transfer (gate-to-source) and output characteristic curves (IV characteristics) of the selected transistor model. It will then automatically select a quiescent point (Q-point), plot the load line, determine the circuit component values, and calculate the primary amplifier parameters. The calculation results will be displayed in the text box under the heading: "Calculation Results".
The calculation of the amplifier stage is performed in three steps:
1) DC analysis of the amplifier stage (Direct Current analysis)
2) AC analysis of the amplifier stage (Alternating Current analysis)
3) Calculation of the primary amplifier parameters
Figure 4 – Preliminary calculation results for the amplifier stage
The calculation of the amplifier stage is performed in three steps:
1) DC analysis of the amplifier stage (Direct Current analysis)
2) AC analysis of the amplifier stage (Alternating Current analysis)
3) Calculation of the primary amplifier parameters
3. Final amplifier stage calculation (adjusting the calculation parameters)
In step 2, a preliminary calculation of the amplifier stage was performed. During the preliminary stage, the program uses default settings for all parameters. For the final calculation, the amplifier parameters must be adjusted to match the specific operating mode chosen by the user. As an example, let's perform such an adjustment. The parameter settings panel is located on the left, as shown in Figure 5.
Figure 5 – Amplifier settings panel
For example, we need to calculate an amplifier with a supply voltage of VCC = 24 V (note that VCC on the output IV characteristics corresponds to the Vds parameter). In the VCC= input field, enter the value 24 (see Figure 6). By default, the program selects a quiescent point of Ido = 2.134 mA (drain current) at the center of the output characteristics.
Figure 5 – Amplifier settings panel
For example, we need to calculate an amplifier with a supply voltage of VCC = 24 V (note that VCC on the output IV characteristics corresponds to the Vds parameter). In the VCC= input field, enter the value 24 (see Figure 6). By default, the program selects a quiescent point of Ido = 2.134 mA (drain current) at the center of the output characteristics.
Example setting parameters
Assume we need to calculate the amplifier with a quiescent drain current of 1.5 mA. In the Ido= input field, set the value to 1.5m (see Figure 6). Next, move to the line below and set the Vdso value (quiescent drain-source voltage). If we want to achieve the maximum current gain in large-signal mode, it is advisable to place the Vds0 point at the center of the characteristics; in this case, set Vdso = VCC / 2 = 12 V.
Then, move to the next line and set the lower cutoff frequency (the lowest frequency in the passband). The default is FL = 10k (10 kHz), but we want to set it to 15 kHz. In the FL= input field, enter 15k (see Figure 6). Next, move down another line to set the load and generator parameters. The default load resistance is RL = 100M (100 MOhm), but we need to perform the calculation for a load resistance of 1 kOhm. In the RL= input field, enter 1k (see Figure 6).
Then, move to the next line and set the lower cutoff frequency (the lowest frequency in the passband). The default is FL = 10k (10 kHz), but we want to set it to 15 kHz. In the FL= input field, enter 15k (see Figure 6). Next, move down another line to set the load and generator parameters. The default load resistance is RL = 100M (100 MOhm), but we need to perform the calculation for a load resistance of 1 kOhm. In the RL= input field, enter 1k (see Figure 6).
Now, set the input resistance of the stage. For the CS configuration, the input resistance is Rin = Rg (see Figure 1a); for the CD configuration, the input resistance is Rin = R1||R2 (see Figure 1b). It is recommended to choose an input resistance in the range of 10 to 100 kOhm. The program defaults to 50 kOhm, but let’s say we need to calculate for 75 kOhm. In the Rin= input field, enter 75k (75 kOhm, see Figure 6). Note that input resistance is directly proportional to the current gain.
Once all the amplifier design settings are configured, click the "Calculate" button again (see Figure 6). This will provide the final calculation for the amplifier stage.
4. Step-by-step solution
This feature is available only for the activated version of the program. When using this function (see Figure 8), the program generates a detailed (step-by-step) amplifier calculation in MS WORD (.docx) format.
