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logic level converter/The boards in your box/03. The five boards
The boards in your box · 03 of 11

The five boards

Three sizes of one MOSFET circuit in the 27-pack, and two TI chips in the 6-pack. They share one rule — A is the low side, B is the high side — and differ in where the power pins are.

Updated 2026-09-114 min readlogic level converter

Every board, pin for pin

Pick a board and slide through its channels. The pin positions come from the boards' own wiring files, and the outlines are drawn to scale.

Every board, pin for pin
2CH · 27-pack
Board
ChannelA1 ↔ B1
Channels
2
In the box
18 × (27-pack)
Inside
2 × BSS138
A goes to the lower voltage, B to the higher, and a channel is a row. Two channels is exactly SDA and SCL, which is why eighteen of the twenty-seven boards are this one. I²C is the commonest reason anybody needs a converter.

The 27-pack: one circuit, three sizes

The 2CH, 4CH and 6CH boards are the same circuit repeated two, four or six times. The power pins sit in the middle of each row: LV and GND on the A side, HV and GND on the B side. Channels are numbered outwards from there.

The 6-channel converter from above: six small transistors in a column down the middle, each with a resistor either side, and A6, A5, A4, GND, LV, A3, A2, A1 printed down the left edge with B6, B5, B4, GND, HV, B3, B2, B1 down the right.
The 6CH board. Power in the middle, three channels above and three below. The two GND pins are joined on the board.

The two GND pins are the same copper. Wiring both is not required, but it is the easiest way to be sure both of your boards share a ground.

The 6-pack: two chips, one footprint

The TXB0108 and TXS0108 boards are identical from the outside: eight channels, VA and A1–A8 down one edge, VB and B1–B8 down the other. The chip in the middle is what differs, and the title on the silkscreen tells you which is which: TXB0108 [SPI] and TXS0108 [I2C].

The 6-pack beside its teal storage case: three TXS0108 boards labelled I2C and three TXB0108 boards labelled SPI, each a long black board with a chip between two round holes and eight labelled pins down each edge.
Three of each. Keep them in separate compartments of the case — they are easy to mix up and they are not interchangeable.

Two things are different from the MOSFET boards. There is one GND, bottom right on the B side. And the pin opposite it, bottom left, is OE, not a second ground. The next page is about both.

On a breadboard

The holes are on a 2.54 mm grid. With header pins fitted, each board straddles a breadboard's centre channel, A pins on one side and B pins on the other.

When it does not work

The labels on my board seem mirrored compared with the drawing

You are looking at the back. The pin names are printed on the component side, the one with the transistors or the chip on it. The back carries the product name and, on the TXB and TXS, the DISABLE: OE->GND reminder.

Which way round does it go on a breadboard?

Either way works electrically. What matters is that the A row is wired to the 3.3 V board and the B row to the 5 V part. Turn the board so the A labels face your 3.3 V board and the wires stay short and uncrossed.

I only need two channels of a 4CH or an 8-channel board

Leave the unused channels unconnected. On the MOSFET and TXS boards, pull-up resistors hold each unused channel at a steady level, so it does nothing by itself.

Alongside this page
The reference, with the photos of both boxes
Where this goes next

LV, HV and GND come first, and each of them fails differently when it is missing.

Power before signals →

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