Voltage series feedback
Download as PPTX, PDF0 likes1,663 views
This document discusses voltage series feedback amplifiers. It defines voltage series feedback as a voltage amplifier topology where voltage is sampled at the output and mixed at the input. The key properties are: - The voltage gain (Av) is VO/VI and the feedback factor (β) is Vf/Vo. - Input resistance (Rif) increases compared to the open loop input resistance (Ri), where Rif = Ri(1 + βAv). - Output resistance (Rof) decreases compared to the open loop output resistance (Ro), where Rof = Ro/(1 + βAv).
1 of 7
Download to read offline
More Related Content
What's hot (20)
Ad
Similar to Voltage series feedback (20)
Ad
More from PRAVEENA N G (6)
Recently uploaded (20)
Voltage series feedback
- 3. Topologies of Feedback Amplifiers Based on the type of sampling (voltage/current) at the output side Based on the type of mixing (series/shunt) to the input side 1.Voltage-series feedback or series-shunt feedback 2.Current-series feedback or series-series feedback 3.Current-shunt feedback or shunt-series feedback 4.Voltage-shunt feedback or shunt-shunt feedback
- 4. Voltage-series feedback or series-shunt feedback Voltage Amplifier. VCVS Av = 𝑽𝑶 𝑽𝒊 β = 𝑽𝒇 𝑽𝒐 Avf = 𝑽𝑶 𝑽𝒔
- 5. Input Resistance with feedback(𝑹𝒊𝒇) 𝑅𝑖𝑓 = 𝑉𝑠 𝐼𝑖 Apply KVL at the input circuit 𝑉 𝑠 = 𝑉𝑖 + 𝑉𝑓 𝑉 𝑠 = 𝑉𝑖 + β𝑉 𝑜 𝑉 𝑠 = 𝑉𝑖 + β𝐴𝑣𝑉𝑖 𝑉 𝑠= 𝑉𝑖(1 + β𝐴𝑣) 𝑉 𝑠= 𝐼𝑖𝑅𝑖(1 + β𝐴𝑣) 𝑹𝒊𝒇 = 𝑽𝒔 𝑰𝒊 = 𝑹𝒊(𝟏 + 𝜷𝑨𝒗) 𝑹𝒊𝒇 >> 𝑹𝒊
- 6. Output Resistance with feedback(𝑹𝒐𝒇) REMOVE RL REMOVE SOURCE (Voltage source – Short Circuit, Current Source – Open Circuit ) CONNECT VOTLAGE SOURCE Apply KVL to the output circuit, V = I𝑹𝒐 + 𝐴𝑣𝑉𝑖 --------------- (1)
- 7. Output Resistance with feedback(𝑹𝒐𝒇) We know that 𝑉 𝑠 = 𝑉𝑖 + 𝑉𝑓 𝑉𝑖 = − 𝑉𝑓 (𝑉 𝑠 = 0) = -βV ------(2) Sub (2) in (1) V = I𝑅𝑜 − βV𝐴𝑣 V (1 + β𝐴𝑣) = I𝑅𝑜 𝑹𝒐𝒇 = 𝑽 𝑰 = 𝑹𝒐 (𝟏 + 𝜷𝑨𝒗) 𝑹𝒐𝒇 ≪ 𝑹𝒐