The BC-525D is the newest version of our popular bilayer clamp amplifier. Warner Instruments is the only company to supply a high quality instrument specifically designed for research using planar lipid bilayer technology and this device forms an integral component of the BLM Workstation.

Major improvements in this new model include:
• Reduced noise and wider bandwidth
• Improved stability
• Digital hold potential
• AutoZero function
• Digital readout of membrane capacitance
• Multi-step 4-pole Bessel filter
• Capacitance compensation circuitryIntegrating Headstage

BC-525D uses an integrating (capacitive feedback) headstage for high bandwidth, low noise recording. This design also provides the ability to cancel capacitive transients produced when applying a step voltage command to the bilayer. The hybrid circuit used in the headstage has two additional benefits: an increase in speed and a reduction in the reset glitch to less than 1 pA at 1 kHz. Reset duration is 100 µs.

Hold Control
The hold control for the BC-525 has been redesigned to function entirely within the digital domain. This unique approach allows the user to make holding potential adjustments in highly reproducible and discrete steps of 1 and 10 mV, up to ±200 mV. Hold potentials greater than ±200 mV or step sizes greater than 10 mV can be applied at the Command Input BNC’s located on the front and rear panels of the instrument.

AutoZero
The large currents flowing through the low resistance aperture prior to bilayer formation saturates the amplifier input. Under these conditions, junction potential offsets can be easily nullified by using the new AutoZero function. Once armed, the AutoZero cycle measures and compensates for any offset potentials in the conducting pathway. Traditional manual controls remain for making small corrections or for resetting the offset potential without re-activating the AutoZero cycle.

Audio Output
The BC-525 now sports a VCO circuit providing auditory feedback during membrane formation. This feature is selectable from the front panel and an internal speaker is included. An external speaker output is provided on the instrument rear panel.
Capacitance Test
This test circuit has been completely redesigned and is used to monitor the formation of the bilayer membrane. A triangle waveform is applied to the command input and the amplitude of the resulting square wave is proportional to the membrane capacitance. When selected, the membrane capacitance is read directly from the meter.

4-Pole Bessel Filter
The filtering capacity if the instrument has been expanded to include a low pass, 4-pole Bessel filter ranging from 0.05 to 20 kHz in 1-2-5 steps. The internal filter can be bypassed for use with external filtering apparatus and allows realization of the instrument’s full 60 kHz bandwidth.
Capacitance Compensation
Large capacitance transients are cancelled using both fast (0-10 µs) and slow (0-2 ms) controls. Each control provides separate adjustment of both amplitude and time constant. Maximum capacitance compensation is 500 pF.

I/O
Input and output BNC’s have been duplicated or moved to the instrument rear panel except for those requiring user interaction. Front panel BNC’s include Command Input, Vc x 10 and Im Output. Rear panel BNC’s include the headstage connecter, Im Output, Cap Sync, External Reset, Command In, and Gain and Filter telegraphs. A speaker output is also available on the rear panel.