====== Logarithmic amplifier ======
**Carry out all analyses before coming to the lab**

{{:courses:ec330:logamp.png?600}}
  * Use V<sub>cc</sub>=9V; Ignore the additional bias resistor of 3R initially
  * Assuming an ideal opamp, and an ideal exponential transistor, determine the output V<sub>out</sub> and the transistor current I<sub>c</sub> in the circuit in (a-i). What is the range of V<sub>in</sub> over which the circuit functions correctly?
  * Modeling the transistor with a transconductance g<sub>m</sub>, determine the small signal loop gain of the circuit. You can break the loop at the inverting input of the opamp as shown in (a-ii), and assume that the opamp's gain is A(s).
  * Does the loop gain depend on the input voltage V<sub>in</sub>?
  * Build the circuit and verify the functionality determined above. Apply a 1kHz square wave input varying between -0.25V and -2.5V and observe the output.
  * Connect the additional bias resistor and observer the output with bipolar inputs? What is the largest allowable input amplitude?

{{:courses:ec330:logamp1.png?600}}
  * Use V<sub>cc</sub>=9V; Ignore the additional bias resistor of 3R initially
  * Assuming an ideal opamp, and an ideal exponential transistor, determine the output V<sub>out</sub> and the transistor current I<sub>c</sub> in the circuit in (b-i). What is the range of V<sub>in</sub> over which the circuit functions correctly?
  * Modeling the transistor with a transconductance g<sub>m</sub>, determine the small signal loop gain of the circuit. You can break the loop at the inverting input of the opamp as shown in (b-ii), and assume that the opamp's gain is A(s).
  * Does the loop gain depend on the input voltage V<sub>in</sub>? What does it mean for the stability of the circuit?
  * Build the circuit and verify the functionality determined above. Apply a 1kHz square wave input varying between +0.25V and +2.5V and observe the output.
  * Connect the additional bias resistor and observer the output with bipolar inputs? What is the largest allowable input amplitude?

{{:courses:ec330:logamp2.png?600}}
  * Use V<sub>cc</sub>=9V; Ignore the additional bias resistor of 3R initially
  * Assuming an ideal opamp, and an ideal exponential transistor, determine the output V<sub>out</sub> and the transistor current I<sub>c</sub> in the circuit in (c-i). What is the range of V<sub>in</sub> over which the circuit functions correctly?
  * Modeling the transistor with a transconductance g<sub>m</sub>, determine the small signal loop gain of the circuit. You can break the loop at the inverting input of the opamp as shown in (c-ii), and assume that the opamp's gain is A(s).
  * Does the loop gain depend on the input voltage V<sub>in</sub>?
  * Build the circuit and verify the functionality determined above. Apply a 1kHz square wave input varying between +0.25V and +2.5V and observe the output.
  * Connect the additional bias resistor and observer the output with bipolar inputs? What is the largest allowable input amplitude?