Design 2 of RC Coupled BJT CE Amplifier | Electronic Devices and Circuits - 1 in EXTC Engineering | Summary and Q&A

TL;DR

In this video, the design of a C II amplifier with RC coupling is explained, covering steps such as transistor selection, calculation of resistances and capacitances, and finding the Q point.

Key Insights

• 🎅 The appropriate transistor for the C II amplifier design is selected based on the given voltage gain requirement.
• ✋ The value of RC is calculated using the gain formula and the specified values of hf e and hie.
• 😥 The Q point, which represents the operating point of the amplifier, is determined by finding the values of VCEQ and ICQ.
• ⚡ The values of R1 and R2 are calculated using the voltage divider formula, considering the value of Vth and VCC.
• ⚾ The calculation of capacitances involves determining the values of CC1, CC2, and CB, based on the design requirements and the AC equivalent circuit.
• ❓ When standardizing resistances and capacitances, it is important to consider the specifications and select values that are readily available in the market.
• 🌥️ The input and output coupling capacitors should have larger values than the bypass capacitor to ensure proper signal transmission.
• 🧑‍🏭 The stability factor, which represents the stability of the amplifier circuit, is assumed to be 8 in this design.

Transcript

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Questions & Answers

Q: How is the appropriate transistor selected for the C II amplifier design?

The selection of the transistor is based on the given voltage gain requirement, with a value greater than 120. In this case, the BC547C transistor is chosen, as it meets the specified specifications.

Q: How is the value of RC calculated?

The value of RC is calculated using the gain formula AV = -RC/re, where AV is the voltage gain, RC is the resistance, and re is the small signal resistance. By substituting the given AV value, the typical values of hf e and hie, and solving the equation, the value of RC is determined.

Q: How is the Q point determined?

The Q point is determined by finding the values of VCEQ (voltage at the collector-emitter junction) and ICQ (collector current) based on the given input and output requirements. The values are calculated using equations derived from the AC equivalent circuit.

Q: How are the input resistances (R1 and R2) calculated?

The values of R1 and R2 are calculated using the voltage divider formula, considering the value of Vth (threshold voltage) and VCC (supply voltage). The equation is rearranged to solve for the ratio of R2 to the total resistance (R1+R2), which is then used to calculate the individual values of R1 and R2.

Summary & Key Takeaways

• The video explains the step-by-step process of designing a C II amplifier with RC coupling, with a focus on the selection of the appropriate transistor and the calculation of resistances and capacitances.

• The design specifications given include a voltage gain greater than or equal to 120, an expected output of 5 volts, and a lower cutoff frequency of 10 Hertz.

• The video provides detailed explanations for each step of the design process, including calculations for the Q point, resistances, and capacitances.