A Belmont Report

2. BUILD AN AMPLIFIER

⟵ 1. POWER A BOARD

In your kit there should be two eight-legged chips that look quite similar. They both should have a little notch at the “top”. Only one of them will have a polished circle next to that notch. That is the LM741 and it will be used to CONSTRUCT A FILTER. For this step, find the AD620, the instrumentation amplifier. It will not have a polished circle.

Step 3. Place an instrumentation amplifier on the breadboard 

  1. Orient the instrumentation amplifier to align with the top of the board and place across the trench so that each of the “legs” of the amplifier is electrically independent
  2. Center the amplifier between the powered rails

Step 4. Wire the instrumentation amplifier for power 

  1. Wire the positive rail (the one with +5 V) to Pin 7 of the amplifier (+Vs)
  2. Wire the negative rail (the one with –5 V) to Pin 4 (–Vs)
  3. Wire the reference rail (the one with how many volts?) to Pin 5 (REF)

Step 5. Create gain, inputs, and an output for the instrumentation amplifier 

  1. Use RG to connect Pin 1 to Pin 8
    • This will enable the amplifier to increase the difference in voltage by a predetermined amount known as gain
  2. Create two loose wires and insert one into each Pin 2 and Pin 3 
    • These two points will be the inputs across which you DETECT A HEARTBEAT
  3. Wire Pin 6 to a free space to the left of the trench and below the amplifier
    • This output will contain the amplified signal

Check in 

  • The gain, G, of the amplifier is defined by the following formula 

G = (49.4 kohm / RG) + 1

What is the gain of your signal, G, given the measured value of your RG resistor?

3. CONSTRUCT A FILTER ⟶