Input/Output

• Signal Source
  • Force
  • Light
  • Concentration
  • etc.
• Output
  • Analog
  • Digital

Case-wise Discussion

• Amplitude of the transduced signal
• Linearity
• Range
• Difficulty of Manual Procedure

Signal Characteristics

• Typical biological signals are weak
  • Low amplitude
  • High impedance
• Amplification required
• But how?

Direct Amplification

• Amplification using a lab operational amplifier
• Easy to setup
• Prune to electronic noise
  • Imperfect common ground
  • EMI (high input impedance)

Physical Amplification

• Amplification using an intermediate signal
  • Light, sound, etc.
• Examples?

Fluorescence

• Can we measure single-neuron activity more easily?
• Ca²⁺ flows through the membrane when the neuron is excited

Exploiting Calcium Level

• Genetically Encoded Calcium Indicators (GECIs)
• Fluorescence level varies proportionally with