Figure 2. Breadboard electronics. The five parts of the system illustrated in Fig. 1B are shown schematically. A, Rail splitter power supply. An 18-V power supply (wall adaptor) is split by a TLE 2426 rail splitter IC into 9 V, –9 V, and ground. The capactors are C1 = 200 μF and C2 = 1 μF. The dark numbers refer to the pins of the TLE 2426 IC. B, Follower, voltage divider, and differential amplifier circuits to map the range −9 to 9 V onto the range 0 to 3.3 V. The resistor values are R1 = 2200 Ω, R2 = 470 Ω, R3 = 4700 Ω, R4 = 22,000 Ω, R5 = 10,000 Ω, and R6 = 100 Ω. C, Connections to the Teensy 3.6 microcontroller. The output of the previous circuit is fed to pin A0, and the output of pin DAC0 is fed to the next circuit. D, Differential amplifier circuit to transform the output of the microcontroller (0–3.3 V, representing the dynamic clamp current) into a range (±9 V) expected by the intracellular amplifier. The resistor values are R7 = 4700 Ω, R8 = 22,000 Ω, R9 = 10,000 Ω, and R10 = 10,000 Ω. E, Summing amplifier. The voltage command from the DAQ board (representing the current clamp’s specified current) is added to the voltage command from the Teensy microcontroller. The sum is sent to the command input of the intracellular amplifier. Resistors R11, R12, R13, R15, and R16 are 10,000 Ω; resistor R14 is 3300 Ω; and R17 is 4700 Ω.