Make It With Matty

The BBC Model B is one of my favourite retro computers. Even over 40 years after its release, there are still plenty of upgrades available that make using it even more enjoyable. One of the most useful upgrades is a Sideways ROM board , which allows you to install several ROMs at once instead of being limited to the standard motherboard sockets. In this post, I'll walk through installing one into my BBC Model B and show the finished result. What is a Sideways ROM? The BBC Model B stores much of its operating software in ROM (Read Only Memory) chips rather than loading everything from disk. These ROMs can contain things like: BBC BASIC Disk filing systems Utility software Programming languages Diagnostic software As you begin expanding your BBC Micro, you soon run out of ROM sockets. A Sideways ROM board solves this by providing additional ROM sockets, allowing multiple ROMs to remain installed at the same time. Why Install One? Although the BBC Model B is an inc...

The Differentiator Amplifier Final Build A differentiator amplifier is an operational amplifier circuit that produces an output proportional to the rate of change of the input signal. Instead of amplifying the voltage itself, it amplifies how fast the voltage is changing. In simple mathematical terms: Vout = -RC × (dVin/dt) This means: If the input changes slowly → small output If the input changes quickly → large output If the input is constant (DC) → output is zero Why is that powerful? Because many real-world systems care about change, not steady values. The Basic Differentiator Circuit Basic Circuit A basic differentiator uses: One capacitor One resistor One op-amp Key layout: Capacitor in series with the input Resistor in the feedback path Non-inverting input connected to ground This is almost the reverse of the integrator circuit. How the Circuit Works Let’s break it down conceptually. The capacitor allows current to flow only when the input voltage is changing. The faster the ...

The Integrator Amplifier The integrator amplifier  is an operational amplifier circuit that performs a mathematical integration  of the input signal.  Unlike the previous amplifier circuits, the output of an integrator doesn’t simply scale or invert the input. Instead, it accumulates the input over time , producing an output voltage proportional to the area under the input waveform . Integrator circuits are widely used in: Signal processing Waveform generation Analog computing Control systems Audio and synth circuits We’ll start with the theory and maths, then build a real, working integrator on the bench using an LM358. What Is an Integrator Amplifier? An integrator is a modified inverting op-amp circuit where the feedback resistor is replaced with a capacitor . This can be seen in the circuit below. Integrator Amplifier Circuit The basic circuit consists of the following: - Input resistor: R Feedback capacitor: C Non-inverting input tied to ground Output fed...